Whether the bank is easy to rob is determined by the bank type. Banks with one room and three guards are the easiest and thus should be robbed as much as possible. Use the following method to rob these kinds of banks with being chased or getting past two shields. First bribe the cop outside before going into the bank and choking the first guard by the door. Next, head into the vault area and strangle the guard on the left. The other guard will then attack you with his billy club. Make sure to always strangle the guard on the left since he likes using his shotgun if you attack the other guard first.
When robbing big banks start the same way by bribing the cop outside and then strangling the guards inside the main room. Now hurry down toward the vault and also strangle the two guards there. Open the door and blow up the vault. Now take out your Tommy Gun to make short work of the few guards that attack while you’re fleeing the vault. Now run up the stairs and move to the right. Take another right to leave the building and reach your get-away car. You must go to your hangout to receive the money.
Note: The easiest bank to rob is the midtown bank near the apartment that the Corleone’s give you after saving Michael. You’ll receive $50,000 there.