Please, whenever possible, link this post to help out your fellow players.
This is best with 2 players, if possible, to maximize profits.
You'll need an Arcade, here's a list of all of them.
I prefer the Eight Bit Arcade because of its location and accessibility to the Garage, as well as the fact that it makes most preps spawn in the same locations for easier completion of preps.

Here's a list if guides that'll help with getting started with the Diamond Casino Heist:

Scoping Out

Scope Out Guide [Skip to 4:36]
All Access Points
All Points Of Interest / POI

Tip 1:

While doing Casino Heist preps, you can make Lester shut up and show the mission objective faster by giving one of your contacts (Mechanic, Assistant, hell even Brucie) a call, as long as you know the contact you call will pick up the phone and not just leave you ringing.

Tip 2:

[Make sure to call Simeon or Martin and request a job before you start a prep, as you cannot request a job while doing Casino Preps]
In some missions you are unable to call Lester and call the cops off of you. During these missions, you can get the cops off of you for free by calling Simeon or Martin and request a job. Once you get the job, join it.
AS SOON AS YOU JOIN THE JOB, LEAVE AS SOON AS POSSIBLE. If you don't quit, you run the risk of the Host starting the job and therefore cancelling the heist prep.
Once you leave the job, you'll be back in Freemode with no cops on you, and you'll still have your heist prep equipment.

Note:

There are two Access Points that are required for the way I run the heist, in Aggressive and The Big Con (Gruupe Sechs), being the sewer entrance on the right side wall in the first opening, and the tunnel entrance leading into the center of the track.

Scope out the Casino

Look for Artwork and Gold, as they are the best (unless Diamonds are available in the vault. In that case, Diamonds are the best)

Changing vault contents

If you've completed all three approaches (Silent & Sneaky, Aggressive & The Big Con), you'll have unlocked the ability to cancel the Casino Heist by calling Lester. You can use this to cancel the heist if you get Cash, or any Vault Content item you don't want.
If you find the Vault contents and get something you don't want, like Cash, you can call Lester while still in the Casino and cancel the heist. Go back to the Arcade and pay the 25k to start the heist again, and you should have a different item for your Vault Contents.
This will essentially allow you to get a second Vault Content item by trading 25k to start the heist a second time with about 8 minutes of finding and hacking / killing the Casino Security guy and going to the Casino.
If, once again, you get a Vault Content item you don't want, exit the arcade, call Lester & cancel the heist, enter your Arcade, rinse and repeat.

Personally, I cycle between Aggressive and The Big Con (Gruupe Sechs).

Now, because I prefer doing the heist through the Aggressive and The Big Con (Gruupe Sechs) approaches, I have little to no experience doing the Silent & Sneaky approach, and thus will be basing this post off of my personal experience in the other two approaches.
Note I'm not going to go into every single prep mission, mandatory or optional as that would take too much time for me. You can look up the rest of the preps on YouTube or Google. I'm only going over my preferred Gunman, Driver, Hacker, the preps that I prefer to do / prefer not to complete, and how I complete the heist.

Aggressive

Gunman: I prefer Patrick MacReary, 8%. I can't remember the other weapon available, but I know he allows you to choose an LMG with 100 round mags. I prefer to use the LMG. You can unlock by finding him in the back of a police van. Take the van to the objective area by following the yellow marker and you'll unlock him.
Driver: I prefer Karim Denz, 5%, which has decent vehicles. I prefer the Sentinel Classic.
Hacker: I prefer Paige Harris, 9%, which you can unlock by owning a Terrorbyte (which you can unlock by owning a Nightclub).

The preps I prefer to do are:

Unmarked Weapons, Getaway Vehicles, Hacking Device, Thermal Charges, Vault Explosives (I prefer to use a Stromberg while doing this mission), Reinforced Armor, Vault Keycards, Patrol Routes, Duggan Shipments, Security Intel (unlock by owning a penthouse and completing the penthouse missions), and Security Pass.
For the Reinforced Armor, I only do this if I have Gold or Diamonds as it slows you down. I also only do this if I am a low level or if I have low level teammates, because low level = low health. If I have Artwork or Cash I don't do this.
As for the Boring Machine prep, you don't need to have the Boring Machine to access the sewer. All you need to do is have took a picture of it and sent it to Lester during the Scope Out prep.

The Big Con

Gunman: I prefer Karl Abolaji, 5%. He has access to the Mini Uzi (I forget the in-game name) and the double barrel shotgun. I prefer the Mini Uzi. *You're going to be mostly going up to people and meleeing them / knocking them out instead of shooting them, unless you get caught, then you'll be shooting them.
Driver: I prefer Karim Denz, 5%, which has decent vehicles. I prefer the Sentinel Classic.
Hacker: I prefer Paige Harris, 9%, which you can unlock by owning a Terrorbyte (which you can unlock by owning a Nightclub).

The preps I prefer to do are:

Unmarked Weapons, Getaway vehicles, Hacking Device, Entry Disguises (2 preps), Vault Drills, Exit Disguise, Vault Keycards, Patrol Routes, Security Intel, and Security Pass.
I don't do Duggan Shipments as usually use my weapon to melee / knock out the security guards at the Casino, and since a melee is a one hit one kill, regardless of level of armor they're wearing, I don't usually do this mission.
Completing the Yung Ancestor missions allow you to have the Grotti Furia, a supercar, as an extra getaway vehicle, although it spawns in the parking lot which is surrounded by cops. I would not recommend doing this.
Again, 2 players are recommended. Start the Heist, get to the Vault. One of you work on the first main room with the big circle table in the centre while the other one will start hacking whichever doors lead to 2 or 3 Artwork or Gold / Diamond / Cash tables. Always go for the rooms that have more than one cart.
Tip: With Gold / Diamonds, you cannot sprint / run, you can however trot. If you go into First Person and tap / press and hold whatever your sprint / run button is, you'll see your character's weapon / screen shake, indicating that you're trotting. Doing this in First Person is actually faster than Third Person.

There are two was I like to lose the cops

1, through the sewer, and 2, by helicopter (Helicopter Route)
[Disclaimer: This strategy is not recommended if you're trying to get the Elite Challenge, as this will most likely take more than 15 minutes, or however long the given time is.]
Once you are out of the Casino, make it to the road. Drive to the sewer opening by the Casino, and if you don't have a car, just run to said sewer opening.

Note:

If you go back the way you came, or anywhere close to the Casino after you lose the cops, you will gain a wanted level again.
Proceed through the tunnel. You'll find a metal gate that you have to pass under, a small vent on the right side, and another vent on the left.
You'll come across 2 paths. Go up the metal ramp on the left. Proceed all the way down the tunnel and down the escalators and ramp downwards. Cross diagonally over the 2 train tracks into the next tunnel with a dirt floor.
You'll find 2 tunnels, left and right. Take either one. You'll find construction, go straight. After this, you'll see a big room. Go straight, take the immediate right and go up the ramps leading to the opening to the highway. If you dont have a car, get one or two and drive to the Buyer.
​
Links to my other posts, which consist of guides, and other useful things I've found & posted.

Diamond Casino Guide:
So you decided that you wanna rob a casino, great! The Diamond Casino Heist is one of the best ways to earn money, but you're wondering, how do I get started? Well, you're in luck! This guide is going to teach you the ways to get the best out of the Diamond Casino Heist!
Step 1: Arcade
Alright to get started, you’re going to have to own an arcade. Now, it may seem better to go for the arcades on the top of the map to save yourself some cash, however, this will make all the preps much harder, as most of them take place in LS or Sandy Shores.
The best arcade locations are 8-bit ($2,530,000, located in Vinewood) and Videogeddon ($1,875,000, La Mesa). When buying your arcade, none of the upgrades are necessary, as most of them are cosmetic. You’ll have to complete a quick arcade setup mission to access the basement where the diamond casino heist planning board is located.
Step 1.5: Arcade Income
While this isn’t related to the diamond casino heist, I thought I would put this in there. The arcade generates income based on how many games you have, going up to 5k per in-game day (48 min). The game doesn't matter, so you can just buy the cheapest one (Monkey’s Paradise, $90,000) and fill up your arcade with it.
Step 2: Scope out casino
After you’ve finished watching Lester scribble a big mess over the whiteboard, you’ll be able to start the casino heist. Normally, you’ll have to pay a setup cost of 25k, but since it’s your first time doing it, it’ll be free. After you’ve confirmed that you want to start the casino heist, you’ll need to finish the scope out mission. For the scope out mission, you’ll need to take a variety of pictures for Lester in order to unlock entrances for the heist. A full guide is linked here but I’ll sum up the most important ones.

• Staff Lobby: This entrance is arguably the best entrance for the Silent and Sneaky approach. It gives you easy access to the control room where you can get the daily vault easily. It is also the best exit for most approaches as not many guards patrol it. The staff lobby should be around the back of the casino and should look like a white door behind some yellow bollards.
• Security Tunnel: By scoping out this entrance, it gives you the ability to enter the casino as a Gruppe Sechs team for the Big Con. This entrance is the best if not one of the best approaches to the casino heist. The disguise will allow you to go straight to the vault undetected and back up, however, you will be detected when going back out of the casino on the casino access floor, so I would suggest getting some exit disguises to make your escape easier. The security tunnel should look like a big metal garage door with a security camera watching over it under the racetrack.
• Sewers: The sewers allow you to burrow down right into the vault access floor giving you easy access as you are right next to the vault mantrap. The sewer exit, however, is only available in the aggressive approach.
• Roof Terrace: At first glance, the roof terrace may seem like a horrible entrance/exit, however as it turns out, the roof terrace is actually a contender for one of the best aggressive exits. By taking the roof terrace, you can shoot down the guards at the racetrack while they're not being able to shoot back and then parachute down.

You’ll only need to do this mission once, and it will be completed for all future casino heists.
Step 3: Vault Contents
The vault contents mission is pretty easy. You’ll be given the rough location of a Duggan security guard, once you find him, you can either hack him, which can take some time but you won’t get the cops on you if you do it right, or you can kill him and grab the phone, which will save you some time but you’ll need to lose the cops before you can enter the casino.
After you’ve entered the casino, you’ll need to bring out the sightseer app on your phone to find a wifi signal. After you’ve located the wifi signal, you’ll need to figure out the vault contents. Beware that you only have a limited time to do this (2 min).
Since it’s probably your first time, I would recommend that you go through every camera to scope out each POI. The target will be cash since it’s your first time, which has a payout of 2.1 mil on normal. The first time will always be cash (payout of $2,115,000 on normal), but if it’s not your first time, the targets can be either cash, artwork (payout of $2,350,000 on normal) or gold (payout of $2,585,000 on normal).
There is a 4th target, which is diamonds (payout of $3,257,100 on normal) however this vault content is only available for special occasions and has been removed from the vault contents.
If you do the heist on hard by doing the same approach after you’ve done another one, the payout will be 10% larger. If you’ve completed all 3 approaches to the heist, you can cancel the heist which can be helpful if you’ve got a bad target. Link to this is here.
Step 4: Selecting your approach
Once you’ve finished the vault contents mission, you’ll be able to select your approach.
There are 3 approaches to the diamond casino heist. Silent and Sneaky, The Big Con and Aggressive.
For beginners, I would recommend alternating between Big Con and Aggressive, because those are the easiest ones. For Big Con, choose the Gruppe Sechs disguise for the easiest entry. Aggressive is good for newer players however it does end up in a lot of money loss. After you’ve got the gist of it, alternate to doing Silent and Sneaky in place of aggressive for a bigger payout.
Step 5: Selecting your support crew
After you’ve selected your approach, you’ll need to select your support crew before you can do any of the prep missions.
Selecting your support crew is very simple. You’ll need a gunman to source guns, a driver to source cars, and a hacker to delay the nerve agent inside the vault.
Selecting your support crew depends on the approach and target in the vault. For Big Con, SnS, any target EXCEPT for art, you’ll want the worst gunman (Karl Abolaji, take his Micro SMG on big con, heavy revolver on aggressive and on SnS the choice is up to you), the worst driver (Karim Denz, take his sentinel classic) and the best hacker available to you, for most people, this will be Paige Harris (unlocked when the Terrorbyte is purchased, gives 3:25 in the vault when undetected and 2:23 detected).
For aggressive, you’ll still want to have the worst driver and best hacker, however, the gunman is up to you since you’ll be using guns a lot. I normally go with Charlie Reed (unlocked when purchasing a hangar), he takes a 7% cut (2% more than Karl) and gives you an assault SMG, however, you can get by with Karl, as every gunman gives you an SMG to go along with another weapon, which is still a perfectly fine weapon.
For Big Con, SnS and the target is Art, if you and your heist partner can both hack very well, you can get by with Yohan Blair (takes a 5% cut and gives you 2:51 in the vault if you are undetected and 2:01 if you are).
Step 5.5: Secret heist crew members
There are 2 hidden heist crew members that can’t be unlocked by purchasing a business like most heist crew members. There 2 are Patrick McReary and Avi Schwartzman. Patrick McReary is a gunman who takes an 8% cut and gives the choice a Combat MG or an Assault Shotgun in aggressive. Avi Schwartzman is a hacker that takes a 10% cut and gives 3:30 undetected in the vault and gives 2:22 if you are detected. To unlock Patrick, he spawns as a random event around the map. He spawns in a police car that you will need to hijack. A guide is linked here. To unlock Avi, you’ll need to destroy 50 signal jammers that are located around the map. A guide is linked here.
Step 6: Prep Missions
Now that you’ve selected your support crew, you’ll be presented with a plethora of prep missions. Some mandatory and some optional. To complete these missions, I suggest that you use a Kuruma, Buzzard, or Oppressor Mk2 to make your life easier. In some prep missions, you will not be able to call Lester, so be prepared. All of the missions can be done solo but it makes it easier if you have a friend with you to help you out.
Now onto the optional prep missions. Optional prep missions, are, as the name suggests, optional. The optional prep you should do depends on the approach. If you own a penthouse and have completed all of the missions, you will gain access to the security intel mission. It’s very easy to complete and you will only need to do it once. A nice trick is that the gauntlet actually spawns when you start the mission, not when the cutscene is triggered, so you can just shoot the driver and take the gauntlet. A guide will be linked below.
Let’s start with Silent and Sneaky. For Silent and Sneaky, the optional prep missions depend on your skill level. If you’re an experienced player, you don’t need to do much, only level 2 security passes. Power drills you can do if you think you have enough time. However, if you are a very new player, I’d recommend that you do patrol routes, Duggan shipments (you only need to destroy 3 to get rid of their bulletproof helmets), level 2 security passes, emp device and infiltration suits and power drills if you think you have enough time. If you do all these, the heist should be a breeze.
Going onto the Big Con, if you’re doing Gruppe Sechs, you don't need to do much. You only need to go through one door if you exit out the staff door, so you can decide if you want to do level 2 security passes or not. Patrol routes do make things easier, however are not necessary. Again, only do power drills if you think you have enough time. Make sure you do exit disguises. Noose and firefighter are exactly the same, so do firefighters since it has an easier mission.
For aggressive, again, patrol routes make it easier but are never necessary. Make sure to do Duggan shipments. You can solo it, but it will be much easier with another person. If you don’t get them all you can just close the game and you’ll be able to do the mission again. Reinforced armor allows you to take more damage, so I would recommend it even if it makes you slower. Be sure to also do boring machine as it allows you to enter through the sewers. Make sure to also do level 2 security passes unless you really like hacking doors.
Step 7: Finding people to play with
Now that you’ve completed all your required prep missions, you need some people to play with. If you don’t have any friends to play with, I recommend checking out HeistTeams or the GTAO Discord LFG Channels to find people to play with. Make sure to have good communication between your teammates otherwise the heist will be in chaos.
Step 8: Completing the heist
Now that you’ve got a solid heist crew waiting to grab all of that sweet loot out of the casino’s vault, you’ll be able to start the heist. If you're doing aggressive, the plan is pretty simple, shoot your way in, grab the loot, then shoot your way out. The easiest entry for aggressive is sewers, and the easiest exit is the eastern roof terrace. If you exit through the staff lobby, you’ll get shot a ton when going over the racetrack, however, if you exit through the roof terrace, you can shoot the guys behind the stones on the racetrack then safely parachute down.
For The Big Con, I’m going to assume you’re doing the Gruppe Sechs approach. By doing the Gruppe Sechs approach, you can pretty much waltz into the vault and back out of it, just be careful that this has some limitations. When going back up the stairwell/elevator to the casino access floor, the guards will have checked the vault and know it’s been robbed, so you disguise ain't gonna work anymore. I strongly suggest getting exit disguises, as they will greatly help your escape. The easiest exit for this is the staff lobby.
For SnS, I’m not really going to go into too much detail here because there’s a full video linked below. What I will talk about is when to use the emp (If you did the prep mission). I recommend emp’ing when you’re at the vault access floor, allowing you to waltz into the mantrap, or when you're coming back up to the casino access floor and are in the mantrap. Be warned that if you decide to get the daily vault when you trigger the emp, the emp’s timer will run out before you can get to your exit, so plan ahead. The easiest entrance for this is the staff lobby and the easiest exit is also the staff lobby.
Tips and tricks to complete the heist

• If you are disguised, do not bump into any of the guards. They will detect you and start shooting.
• In the control room, there is a button that you can press to open the door to the daily vault. One person has to hold the button while the other goes in and grabs the cash. This can be done with any approach.
• Running and jumping is faster than just running normally, use this to your advantage while inside the vault.
• Running in first person is actually faster than 3rd, so use this to your advantage when trying to knock out guards.
• Don’t bother trying to escape the cops by hiding in an alley or something, either take your car into the sewers down by the LS river or take the heli that usually spawns on top of the police station. The sewers will result in you losing less money, however will be much slower. I will link both of these methods below in the useful media section.
• Normally when exiting the casino from the staff lobby without any disguise, you’ll need to knock out a guard to the left of the swat fan to your right, before hugging the race track wall and then dropping down. I have found that sometimes if you run, the guard will hear you and detect you, causing you to get shot at. To prevent this, walk up to him making sure you stay out of his FOV then knock him out.
• You walk much faster in the casino if you are in first person, making the vault contents mission much easier.
• In prep missions, you can change any accessory (glasses, hat, ect.) to lose 1 star which is useful on missions where you can’t call Lester to remove your wanted level.
• On some missions, you can lose the cops by entering your Terrorbyte/MOC/Avenger.
• On some missions, you can lose the cops if you accept Lester’s apartment heist invite. This only works if you have a heist active.
• In the hacking device mission where you have to infiltrate the FIB building, you walk a lot faster if you aim down sights on any gun, however, if you go into any agent’s LOS you will get detected instantly, so be careful when using this trick.
• You can upgrade your getaway vehicles in the arcade by getting in them and pressing the button shown on the prompt that appears on the top left.

Useful media

• Practice casino fingerprint hacking
• Easiest way to complete Silent and Sneaky
• Casino Heist Big Con Gruppe Sechs
• Casino Heist Aggressive Sewer Entrance
• How to make the most money out of the Diamond Casino Heist
• Casino Heist Sewer Escape
• Casino Heist Heli Escape
• Security Intel

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Diamond Casino Heist FAQ
Welcome to the Diamond Casino Heist FAQ! This thread is going to go through all of the new changes and content added to the Casino Heist DLC. The information in this thread is up to date as of 28/7/2020.
Release Date
Announced on December 5th and released on December 12th, 2019, the Diamond Casino Heist is the latest DLC to come to GTA Online as of July 25th, 2020. This DLC adds a bunch of new content, including new vehicles, properties, vehicles, and a brand new heist!
New Content
Vehicles:
Maxwell Asbo (SSASA): $306,000 - $408,000
Karin Everon (SSASA): $1,106,250 - $1,475,000
Lampadati Komoda (Legendary): $1,275,000 - $1,700,000
Vapid Retinue Mk II (SSASA): $1,215,000 - $1,615,000
Ubermacht Rebla GTS (Legendary): $1,175,000
Maxwell Vagrant (SSASA): $1,660,500 - $2,214,600
Grotti Furia (Legendary): $2,055,000 - $2,740,000
RUNE Zhaba (Warstock): $1,800,000 - $2,400,000
Karin Sultan Classic (SSASA): $1,288,500 - $1,718,000
Nagasaki Outlaw (SSASA): $951,000 - $1,268,000
Declasse Drift Yosemite (SSASA): $981,000 - $1,308,000
Dinka Sugoi (SSASA): $918,000 - $1,224,000
Dinka Blista Kanjo (SSASA): $435,000 - $580,000
Nagasaki Strider (Legendary): $502,000 - $670,000
Dewbauchee JB 700W (Warstock): $1,470,000
Overflod Imorgon (Legendary): $2,165,500
Albany V-STR (Legendary): $1,285,000
Progen PR4 (Legendary): $3,515,000
Ocelot R88 (Legendary): $3,115,000
Nagasaki Blazer Lifeguard (Warstock): $62,000
Brute Boxville (Warstock): $298,500 - $398,000
Declasse Bugstars Burrito (Warstock): $450,000 - $598,000
MTL Fire Truck (Warstock): $2,471,250 - $3,295,000
Declasse Lifeguard (Warstock): $865,000
Brute Stockade (Warstock): $1,680,000 - $2,240,000
Weapons
Ceramic Pistol (Ammunation): $20,000
Navy Revolver (Unlocked after finishing the Los Santos Slasher treasure hunt): Free
Properties
The release of the Diamond Casino Heist DLC introduces a new property: arcades. Arcades are a passive business that allows you to host the diamond casino heist. The maximum daily income of the arcade is $5,000.
They are purchasable from Mmazebankforclosures at 6 different locations. The cheapest is at $1,235,000 (Pixel Pete’s, Paleto Bay) and the most expensive being at $2,530,000 (8-bit, Vinewood Hills).
Customization options on offer are 2 arcade styles, $290,000 - $470,000, 8 mural options, $50,500 - $107,500, 8 floor options, $78,000 - $165,000, 8 neon art styles, $107,500 - $320,000, personal quarters, $150,000, high score screens, $295,000 and a garage $215,000. 2 extra options are available to purchase from the arcade computer, which are the master control terminal, $1,740,000 and the drone station, $1,460,000. A variety of arcade games are also available to purchase, ranging from $90,000 to $420,000.
Credits
u/Pepperooney_ for adding a bunch of info on the tips and tricks section
u/what_it_dooo for suggesting the roof terrace and the hacking device trick

I haven't seen a good comprehensive guide for this, despite it being the best money making method in the game, so I thought I'd write a guide about it.

What is the Casino Heist and why should I do it?

The Casino Heist is semi-challenging PvE content for 2-4 players. As of August 2020 it's the best paying grind in the game, paying out $1.5-$2 million split between heist members every hour and a half. If you're doing setups with one friend, you're both effectively earning ~$80k per setup mission.
If you have no friends who play GTA:O, try to find a buddy in game or on HeistTeams
It's possible to get even higher payouts, but discussing glitches is against the rules of this subreddit; go to gtaglitches for that stuff.

Getting Started

To do the Casino Heist you need an Arcade, preferably Eight-Bit (Vinewood) or Videogeddon (La Mesa) as they're the closest to the Casino and setup missions.
Not required, but strongly recommended as they'll make setup missions much easier:

• A good gun, such as Special Carbine
• A bulletproof car for gunfights, such as Armored Kuruma
• An aircraft with homing missiles, such as Buzzard Attack Chopper or Oppressor Mk2

Scoping and Vault Contents

All Points of Interest
All Access Points
Cash has the worst payout (up to $2.1 mil). You will always get cash the first time you host the Casino Heist.
Art has middling payout (up to $2.3 mil) but is very fast to steal, which means you can get detected, or hit the vault with fewer players, and still get the maximum take.
Gold is like cash but gives much better payout (up to $2.6 mil), with the disadvantage of making you run slightly slower when you leave the vault.
Diamonds only appear during special events, but have the highest payout for vault contents (up to $3.6 mil).

Choosing Approaches

The Big Con is the best approach, since the security tunnel entrance + Gruppe Sechs disguise takes you straight to the vault. Always choose it when possible.
Silent & Sneaky is like The Big Con, but is more difficult and takes longer.
Aggressive is relatively fast, but gives less time in the vault, making it much harder to get the maximum take for any target except Art.
In general, you should choose Aggressive for Art, The Big Con for other targets, and Silent & Sneaky only as a last resort. You should also choose Hard mode whenever possible as it gives you a 25% higher take.

Support Crew

Your Hacker is the most important support crew member, as they determine how long you have in the vault, and therefore your maximum take. My go-to is Paige Harris, who you unlock by owning a Terrorbyte. Avi Schwartzman is equally good and can be unlocked by destroying all Signal Jammers. If you don't have either of them, Christian Feltz is a decent stopgap measure; just be aware you'll have a good chance of missing out on profits.
The Driver determines your getaway vehicles, and is largely irrelevant since most people ignore the getaway vehicles and jack a car or a helicopter for their escape. I always go with Karim Denz and source the Sentinel Classic. It's only worth getting a more expensive driver if you want to unlock a car's trade price.
The Gunman determines the weapons you'll be using in the run. Again, mostly irrelevant, since Karl Abolaji's weapon loadouts are good enough even for a Hard Aggressive approach. Only get a more expensive gunman if you're going Aggressive and aren't confident in your headshotting skills or those of your crew.

Optional Preps

I don't recommend paying to skip any of the preps, because it eats significantly into your profits, and unlike MC/bunker missions, you can't easily make back the cost by doing other missions in that time.

• Security Passes

Mandatory for every approach. Remember to get level 2 security passes, not level 1. The mission is very easy and saves you from having to do lots of annoying hacking minigames during the final heist.

• Duggan Shipments

This is mandatory for Aggressive and Silent and Sneaky, as destroying at least 3 shipments will remove the bulletproof helmets from guards and allow them to be headshotted. Most people also do this for Big Con just to be safe. Having at least one other player in your organization, as well as a Buzzard or Oppressor Mk2, makes this mission very easy.

• Security Intel

Unlocked after completing all Casino Penthouse missions, this is a once-off mission that reveals security cameras on the radar on all future casino heists. Do it when you unlock it.

• Patrol Routes

Reveals guards on your radar. Not required, but useful on every approach, especially Silent & Sneaky. Do this if you have time.

• EMP (Silent & Sneaky only)

This mission is relatively easy and the EMP saves a lot of headaches in a Silent & Sneaky run. Not required, but worth taking the time to do.

• Boring Machine (Aggressive only)

This unlocks the best entry route for the Aggressive approach where you tunnel straight to the vault. Not required (Staff Lobby is almost as fast) but it makes the approach to the vault very easy.

• Power Drills

Don't bother with this mission, other than to play through it once or twice for fun. The money from the deposit boxes isn't worth your time.

• Exit Disguise (Big Con only)

These missions are annoying and the disguises aren't that helpful. Collecting all playing cards gives you a permanent exit disguise you can use; I recommend doing that instead and never having to worry about this prep.

• Infiltration Suits (Silent & Sneaky only)

This mission gives you night vision. Basically, it's only useful if you plan on using the EMP but don't know the casino floor layout. Do it the first time you do a Silent & Sneaky run; by the second time, you should be experienced enough that you don't need it.

• Reinforced Armor (Aggressive only)

This unlocks new outfits that reduce the damage you take during the heist finale. Personally, I hate this prep, because a) the mission is annoying, b) the finale is easy enough without it, and c) the armored outfits are ugly. Do it if you aren't confident in your shooting skills, or if you plan to do the heist with only two players.

Finale Screen

Buyer: Always choose the High Level buyer for the best payout. The only difference is that you have to drive or fly a few more miles after you lose the cops -- more than worth the extra percentage of the cut.
Decoy: This makes the helicopter getaway slightly easier on the Aggressive approach, or if you screw up either of the other two approaches. I don't think it's worth the extra cost, but it could be worth it if you find yourself constantly having trouble getting to the helicopter.
Clean Vehicle: Completely useless. Don't bother.

The Big Con

Entrance: Security Tunnel
Exit: Staff Lobby

• Go straight to the vault. Take your sweet time plundering it.
• Take the stairs on the way up. You want to take the long corridor looping around the back, pass by the laundry room and pick up your exit disguises if they're there, then make a run for the staff lobby exit.
• You will be busted if guards or cameras see you. The guards in the security office can't see you through the bulletproof glass, but you can be seen through the glass panels in the doors.
• Melee kill the patrolling guards from behind and run through the cameras without staying in their cone of vision for too long.
• Once you're out of the staff lobby exit, there will be a NOOSE van to your right. Head past it, melee killing the guards, and make your way to the main road. From there, you can run to your getaway vehicles or jack a random car off the road.

Silent & Sneaky

Entrance: Staff Lobby
Exit: Staff Lobby

• Take your time and have one person go ahead at a time. You want to make sure that you're headshotting guards with your silenced machine pistol, and using the stun gun on all cameras you pass by. If there are two guards next to each other, shoot them both in quick succession.
• You will be busted if guards or cameras see you. The guards in the security office can't see you through the bulletproof glass, but you can be seen through the glass panels in the doors.
• The daily take is worth getting if you have time.
• You can use the Nano Drone in your inventory to shoot a tranquilizer dart. This is most useful on the guard patrolling the stairwell. Have your teammate wedge the door open, then fly the drone through the gap and down the stairs to knock the guard out.
• If you got the EMP, you can use the SecuroServ app on your phone to activate it. This gives you 1 minute to book it and run past all guards, security doors, and cameras on a floor.
• Once you're out of the staff lobby exit, there will be a NOOSE van to your right. Head past it, killing the guards, and make your way to the main road. From there, you can run to your getaway vehicles or jack a random car off the road.

Aggressive

Entrance: Sewer or Staff Lobby
Exit: Staff Lobby

• This is a straightforward gunfight. Just move from cover to cover and shoot everything that moves.
• As always, use headshots to get instant kills. Even if you did all Duggan shipments and got an expensive gunman, the guards can take a ridiculous number of bullets to center of mass, so it's faster to aim for the head and take them out instantly.
• The guards respawn continually, so it isn't possible to completely clear a floor out. Just keep moving.
• The daily take is worth getting if you have time.
• When exiting through the staff lobby, don't go straight through the security office or you'll be shot to pieces. Take the long way around instead.
• Once you're out of the staff lobby exit, jump the fence to the racetrack and run straight across. If there are any cars in the parking lot to your left, jack them and drive out. Otherwise, keep going and jump the fence to the main road. From there, you can run to your getaway vehicles or jack a random car off the road.

The Getaway

No matter which approach you take, you'll eventually end up outside the casino, on the main road, with a 5 star wanted level. There are two main strategies people use here.

• Sewer Tunnel: Directly south of the racetrack, in the storm drain, is the entrance of the sewer tunnel that Michael and Franklin escape through in story mode. If you drive in here and keep going, you'll eventually start losing your wanted level. Get out of the car and wait in the sewer until you're all clean. From there, it's an easy drive to the buyer -- just don't drive near the casino or you'll be wanted by the cops again. This is a safe but slow getaway.
• Police Station Helicopter: Over the overpass to the west, directly across the highway from the casino, is the Vinewood Hills police station. It's possible to drive to the back of the building and climb from the grass patch up to the roof. There, you can climb the roof fixtures to get to the helipad, where a police helicopter usually spawns. Once everyone is in the helicopter, you can use it to evade the cops. This is a quick but more risky getaway, since the helicopter occasionally doesn't spawn, and you can get shot during the drive or fall off the roof if you're unlucky.

Bugs

• Permanent Wanted Level

Bug: You're in a getaway vehicle far from any cops, but your wanted level won't go away. This happens because one of your heist teammates has high ping and the game is having trouble syncing your wanted levels.
Fix: Have everyone get out of the vehicle and wait until the bug goes away. If you're in a helicopter with no safe place to land, the offending teammate(s) may have to parachute out.

• Guards Spawning Late

Bug: On Silent & Sneaky, guards take a few moments to spawn in after you disable the metal detector.
Fix: Don't go through the metal detector or shoot anyone until the guards finish spawning in.

• Frozen Guard Patrols / Bugged Camera Movement

Bug: The guards in the casino aren't moving, and the cameras have weird movement patterns or are facing towards walls.
Fix: Just keep going; this bug actually makes Silent & Sneaky / Big Con easier most of the time. If there's a frozen guard you can't get past, use the Nano Drone.

• Disappearing Vision Cones During Getaway

Bug: You're getting away from the casino undetected when the vision cones suddenly disappear from your radar. Despite this, the police aren't coming after you.
Fix: This is a visual glitch and you haven't actually been discovered. Just keep going.

• Spectator Leaving

Bug: Someone joins as a spectator, then leaves. You screw up the heist and have to restart. Then you fail the heist because "Your heist team quit."
Fix: Suck it up and reset.

• Silent & Sneaky Body Found

Bug: You're suddenly busted because a body was found... even if you haven't killed anyone yet.
Fix: Suck it up and reset.

• Uncollectable Heist Prep Equipment

Bug: You're doing heist prep mission with a friend, and you can't pick up the equipment because "you can't steal heist prep while on a heist prep mission."
Fix: Suck it up and reset.

• Heist Prep Vehicle Not Registering

Bug: You collect a heist prep vehicle and drive to your arcade, but it doesn't trigger the end of the mission.
Fix: Suck it up and reset.
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Hope someone out there finds this guide helpful. Comments and suggestions appreciated.