Before you even consider stealth you will need to ask yourself this, "Am I patient enough?", as sometimes stealthing can take up to 15 minutes. My personal best time is 1 minute and 12 seconds, but I use a different method of stealthing that most people dont use.
Before you even join a lobby, you will need a stealth weapon. The Chimano 88 Pistol is the first pistol in the game, and is given free at the start, and isn't actually a hlaf bad peice of kit, you get a free Standard Issue Suppresor too for it, so that is an extremely worthwhile investment.
There are other stealth loadouts, but the Chimano 88 Pistol is all you will really need for now.

Upon joining a lobby, like so;
You will want to ask if you are stealthing, they may say "Going loud." which means they aren't and they are just running in and shooting everything, which means you will need armour, or they may say yes. If so, let them know if you haven't stealthed it before, and ask them what they want you to do, and that means answering questions that may seem a little noobish vets!
When stealthing you want to get your detection risk as low as possible without dropping a silencer, the lowest is 3, and the highest is 75, as you may have guessed already.
This can be made lower by raising the Concealment stat, this means its easier to hide the gun, or switching to lower armour, like the suit, which is almost a given in stealth.
Having the Dectection Risk lower will slow down the rate at which you are spotted by guards and allow you to get closer before they start to detect you, that still doesn't mean you can hug guards though, you still have to keep your distance, but you may get closer.

In the prep lobby, you should ask if teammates want you to bring something in specific, like another ECM or the OVE9000 Saw.
This is when you can talk before you start the heist, this is the best time to say if you dont know how to stealth the heist, or even at all.

This is where the magic happens. This is when you need to co-operate, if you can't co-operate, then this game isn't for you. First thing I personally do is check where the security door is, this is where the camera operator is, and upon killing him, will disable all the cameras on the map. I check where it is by looking through this window;
The door isn't visible above the cover, so means it must be in the back, so make sure you inform your teammates.The door looks like this;
The different ways to open it have been labeled with letters. A) is the best method of opening, but requires a high level Ghost skill to be aced called "ECM Overdrive", which grants the ability to open security doors with the ECM Jammer. B) is the Keycard, which can be dropped by the manager, or found on his back desk, this can be a more difficult method, if the manager doesn't have the keycard, but is less risky than drilling or sawing. C) is Satchel Charges, which are a Technician skill, but alerts civs and guards upon exploding. Doors like this require 3 charges, which is half of the total Technician's amount. D) is the loudest method but can also be the quickest, but is almost pointless when stealthing, as it alerts almost every character on the map. E) is the other stealth possibility but is extremely hard to keep hidden as it takes about 4 minutes without upgrades, and attracts guards and civs, and can be easily seen. Inside the room will be a guard and camera access.
A) is the camera access point, which can be useful. When interacted with it shows the viewpoint of cameras, which can be turned slightly and zoomed out with the scroll wheel, if someone requests, stay on the cameras, as they can spot guards you see, which allows the whole team to see them, even through walls. B) is the dead guard, when a guard is killed they have a pager which requires answering, otherwise the alarm is triggered. If a pagers timer is running lower it will flash, which means it needs answering soon. A pager has a timer of 12 seconds before it will sound the alarm, and requires 10 seconds to answer, but the 10 second answering period can be done while the pager is flashing, as the alarm period stops. A total of 4 pagers may be answered, after this the alarm will be triggered, as "The Pager Operator Wasn't Convinced By The Answer".

This body can then be bagged, and moved to a location where it cannot be seen, e.g. The bin at the right door, or behind in the car park, hidden behind some cars.

If your team says they are "Rushing", you need to wait until they say so, then run in, kill the guards, and tie as many civs as you can before the pagers pop up, if the owner of the ECM has the ECM Specialist skill, which delays pagers for the duration of the ECM. When the ECM runs out you have to leave whatever you are doing and answer a pager, if two people are answering a pager then one may let go, but make sure you both don't let go, because otherwise that will trigger the alarm.

If the rush fails, and the alarm is tripped, teammates may want to suicide, so if they say this, then they will want to kill themselves to restart the heist. Don't attempt to revive people, otherwise you may risk getting kicked from the lobby, which you don't want.

After rushing, there will be a long-ish wait period of around 5 minutes, so you probably want to kill some time by doing these;
Collecting packages, this will provide free attachments if you have the Gage Courier DLC, and an xp boost, whether or not you have the DLC.

Opening the ATMs with an ECM or the Saw, this will give $20,000 or $26,800 with Dead Presidents, which is roughly $4,000 spending cash (Divide the total Payday by 5), but requires a spare ECM, or the Saw.

But avoid boarding, as it is annoying, as teammates may need to use that window to move bags. If you HAVE to board, break them afterwards, it takes 15 shots, unless you have a shotgun... Obviously.

A good thing to do is to check the drill and relay the time to your teammates, as they may be getting impatient waiting for the vault to open.

When inside the vault, a Saw can cut open the Deposit Boxes, which can contain bags (Money or Gold), or Loose Cash (Rings, Cash Wads, Necklaces, Gold Bars, etc.). If there is a Saw, then dont bother picking the Deposit Boxes, as you could be moving bags, but if there is no Saw, and you are desperate for money, you can pick the deposit boxes. This can take up to 15 minutes, as it takes 20 seconds per box, or 10 with the Lockpicking Expert skill aced, but can make you at least an extra 100k, maybe up to 300k on Death Wish. A good tip to not annoy people is to not hug the player with the saw, as it can irritate them since they can't see where they are sawing, and there is no rush to get the loot, its not like theres any cops pestering you. Even if there is, you still shouldn't hug them, as your job becomes keeping the cops out of the vault, but hopefully you shouldn't need that as you are reading a guide about stealthing the said bank.
And just an FYI, a bottom tier Ghost skill is Dead Presidents, which increases the value of Loose Cash, by 10% basic, and a total of 30%, so make sure you ask if someone has this skill, and if they do let them grab all the Loose Cash, as that will be a boost to the teams total Payday.

This should be all you need to know to successfully stealth a Bank Heist with an experienced team, at least after a couple of tries.

You can now enjoy the easy xp, money and payday;

This should be all you need to know to successfully stealth a Bank Heist with an experienced team, at least after a couple of tries. This is my first guide, and if anything is inaccurate, or not quite right, please let me know, and Ill update it. Thanks for reading this far xD Cause it was a long one.