You'd best not camp. Try to rotate, find two or three good spots to snipe from, and keep the bad guys guessing. The enemy CAN see your little red dot, so try to keep it out of sight as often as possible. It is the ultimate giveaway. When counter-sniping, do NOT stand still.
Snipers love stationary targets.
A good technique is to stay behind a wall, charge up your rifle, and strafe into view. You pop up unexpectedly, you're moving, therefore more difficult to hit, and your gun is charged and ready to kill. When you've been caught with your pants down. If an hwg 0r soldier sneaks up on you unawares, it's a much better idea to just unzoom and boogie. You may take 'em out with a rifle shot, if you're lucky, but usually you just end up dead.