i'm think i'm beginning to get the hang of it.
like always, cover is key. if you can have a building or rock on one side of you and a bush in front of you, you're golden. knowing the map is key and they set up a lot of these things around the map.
if you can wait for your reticle to really shrink, you'll be far more accurate. don't just shoot when the gun is reloaded.
the RB targeting only works when you're in 3rd person view and is meant for shooting on the go. so you wait until the target is red and then you tap RB. he'll say person is targeted and then say person is locked. if locked, you'll score a hit. if you shoot while targeted, it's pretty hit or miss.
spotlight as many people as possible. it's pretty satisfying to spot someone and then see your teammates rain down on them.
and of course, hunt in packs. 2:1 rarely works.
also, keep in mind that you can turn your viewpoint far faster than your turret actually turns.