Well, you need a weapon. Bring atleast 5 mags as you will never know how you ran out of ammo, bring a crew, some bandages and stimpacks. These are essential resources, just ask
@HomerWithTopHat. I usually bring a shotgun or a rifle, only bring a pistol when you know you're not going to win.
If you know you're not going to win then don't even bother, you'll most likely break 3.4 as there is no chance of you escaping with a pistol. Quote from
3.4 Putting your Life at Risk - Risks are deemed to be unreasonable when it can’t be appropriately and effectively justified; for example, if a player was to rob the bank and fail, leading to their death, that player would be expected to demonstrate to an administrator that they had a realistic and reasonable plan and/or mind-set to succeed.
Onto the actual question however, I always bring 20 stimpacks and at least 5-10 bandages, I bring a fully loaded Sako 92 with 5 fully loaded magazines, make sure you have at least 4/5 regeneration (5 is optional but 4 is still good enough) The Sako 92 is very good at sniping at long range, either stay in the vault or go on the roof (bringing a Sako 92 I highly recommend you go on the roof) At least have two people go inside the vault.
Tactics: Hide your vehicle(s) so the police won't expect to be that many people inside the bank, you should try and ambush them and always, ALWAYS go for the S.W.A.T first since they have the heavy weapons. If possible, snipe the S.W.A.T officer on the roof, I always hide and then ambush them when the cops don't expect me (Always fun seeing them run away
) If you're under attack and you think you may die, jump from the roof to the 2nd floor of the city garage, if you fail the jump and land near the back end of the bank then go behind and wait, officers may have seen you.
