Stay
behind the hills. Just stick your gun over the hill just enough so you can see your enemy.
be patient - thats the most important thing you can do. To be a good sniper, you must be patient, if your not patient, your not going to be a good sniper.
switch from spot to spot - like convict said, never stay in the same spot for too long. Get 2-3 kills, then rotate.
conserve your ammo - this also an important thing to do while sniping. You don't want to be 600 maybe 700m's out and run outa ammo. Then you'd have to run back to your spawn or the nearest armory and get some more. Don't take shot-after-shot-after-shot, carefully and patiently, take your shots.
Hope those tips help.
