As a chopper pilot I try and do my best to circle strafe the area I am attacking from a distance of about 75-100 meters.  Makes the gunner's job easier, keeps you moving a little bit to keep infantry from being able to hide in the same place, and it's just indimidating to see a chopper doing a huge 360 from the ground.  You KNOW you're done for.  I always try to spot as much as possible for the gunner so that he's aware of potential threats like tanks and APCs.  Always tilt the nose up a little bit to signal that it's time to TV missile an enemy.   

As a gunner I would appreciate it if the pilot would fly steady and high enough to be out of the way of ground forces but not so high that planes are always seeing you.  Line me up for the TV... don't swoop in for rocket attacks unless you just saw me launch a TV, in which case it's going to be a while before it's reloaded.  Watch what I'm doing... which direction my gun is facing, and pay attention when I spot enemies, as there are two of us capable of attacking. 

The chopper is one of the reasons this game is so much fun!