Take plenty of time to walk the fields and develop a strategy. This is something that rookie teams often fail to do. They plan their primary and somtimes secondary bunkers but dont think the entire game through. If you watch teams like dynasty play they walk the fields calculating the killing zones from every bunker, the most important locations on the field and all the lanes that will need to be closed at whatever times. With strong tactics, a less experienced team can hold their own against a disorganised squad of far more experienced players.
On the other hand, 3 man tournaments are small and will allow a higher degree of free handedness with regard to tactics etc. So you will have to work things out for yourself. Make sure you put up plenty of paint on the break, as Ladyboy says, try and clip out at least one off the break cos then its immediately a 2v3 situation which is a massive advantage.
Take the width and length of the field. Ie, have a player on each tape to cross up and also to watch the tapes. Then have a player in the middle, perhaps try and take the 50 yard bunker and kill from there.
Most important thing though in my opinion is movement and communication. The hardest thing for new players seems to be taking the windows of opportunity that open during the course of the game. dont be afraid to get out of your bunker and take another or mug somebody, its these kind of actions that win you the games. If you just sit back in cover the chances are the opposition will close down on you and lock you down before bunkering you out.
Which tournament is it you'll be playing at btw?