What works well for me is constantly checking the main map, enemies give up their position when they move so pick them off when they are vulnerable.
Another thing is to be very subtle when you mine, dont leave mines in real obvious places, hide them under jeeps, roofs and blind corners. Use the same idea if your playing capture the flag, if the flag is in closed in a building toss some grenades in before you enter, chances are there are some mines.
R2+L2 is very useful in a warhawk, my favorite manuver is just doing a loop when a guy is on my tail, if you do it right they pass you up and you switch positions. But if you want to get good in a warhawk you gotta be good with any given weapon. Also double tapping R2 gives you an instant boost.
Now im prolly going to regret telling this when this is used against me, but I still have some tricks in the bank.