Use Caution and think like it is real.
If you killed someone from a spot and he could come back, Ýou would move, just don't move real far and don't start to move for 2 seconds so his kill cam shows you staying there .Wait for him from a different spot. They usually come firing at the last spot you were in, kill him and move again.After 2 or 3 kills, move slowly to another area and repeat.
If you play core use a silencer and don't be too quick to shoot, if they don't see you always wait to kill them from behind.
Always think about not giving away your position and be aware of your muzzle fire especially if you have a blind side.
Key is to kill and move.
Don't be lured into thinking you have a great spot. After a couple of kills you are going to die if you stay there.