before how to shoot..Know how to stay alive!
It sounds like common sense, but keep in mind -- you're controlling a character that, in some ways, moves like a tank. Strafing, moving, aiming, firing, and trying to do all of these things at once is not easy on a mobile device, and it gets significantly harder when most of the zones have closed and you're down to the last dozen or so players.
Run away and heal up whenever you can. This is fairly good advice at almost any stage in the game, but it becomes absolutely imperative to maintain an edge near the end because it's not a mere possibility but a high probability that there are other players close by that can hear your firefight. Try to disengage as quickly as possible if you can't get a quick 1v1 kill, because whoever's watching you will have the upper hand at aiming if they're standing still (and/or sniping!).
Keep yourself healed and your energy high. This will help you with health regeneration and speed in those last-ditch fights!
Only use your vehicles in the beginning. They're not too difficult to handle, and if you landed in some of the far-off areas, you're going to want something to help you hoof it when zones start closing and you're stuck in areas with a lot of bridges. End game, though, the engine noise just isn't worth the extra speed, especially with a smaller map space to navigate through. Be a sneaky ninja.
Shoot to kill. While spray and pray generally works better in mobile firefights, only shoot when you have to. Gunfire draws attention to you just as much as engine noise does, and someone else is going to want to take advantage of your distraction.
Be careful about when you're looting. In the end game, moving around and looting should be done as sparingly as possible -- and only if you're running low. If you get too greedy and try to loot the body of someone you killed right away, chances are anybody who's been watching will know exactly where you are and can pick you off while you're distracted.
Only move when you have to. Again, this is specifically for endgame only. Early game you should explore, loot, customize your guns, do whatever you need to do. But as the area starts to get smaller, you should be watching the zone carefully and moving to accommodate for that, not to simply run around looking for a fight. It will come to you soon enough without giving the upper hand to someone else! This will also make it easier for you to aim and kill when you don't have to concentrate so much on movement in your first few shots.