The best tactic for when in a gun fight situation. when you are in a game created by yourself, press the "x" button, and press the number "3". this tells your team mates to stick together. then, all you have to do is walk to some where and your whole team follows you. then, if you are in an arms fight, you can hide behind your team mates while they fire, and take an accurate gun and kill the enemies while they are killing your team mates, then you can get lots of kills with out hardly getting damaged.
A tactic for the Counter-Terrorist force. this is the best tactic for the counter terrorist force, because in the counter terrorist force, you have the shields, and if you start your own game, in the options, you can choose for your team mates that they can only use the shields and the grenades and pistols, then you press "x", then "3", then they will follow you with their shields, and there will be a massive wall of counter terrorists that will be indestructible, and you can move in one heave, and while the terrorists are busy shooting at you, when they reload, you can kill them with the whole team firing at once.