Don't save whilst the cheat is active - this is an important one.This is another reason why you should save first, so you can re-load that save game to go back to before you entered the cheat. Most cheats can't be deactivated - re-entering a cheat will often bring up a 'cheat deactivated' message in-game, but in our experience that often leaves the cheat still active, or at least the resulting chaos still well in effect.Always save first so you have a backup just in case.
While entering cheats in GTA 3 is pretty simple, there are always a few things to bear in mind when you're planning on using them in-game. Watch on YouTube GTA 3 cheat codes explained: what you need to know about cheats in Grand Theft Auto 3