What you need to do is go onto free for all because you will get the most amount of kills in this game mode because people spawn all over the place and cod is retarded with their spawn points so people will spawn in front of you or all around you, but watch out because it might be you that gets spawned in infront of someone.

What you need to do is find a pretty highly traffic area in the map you are playing on in just cruise around there going back an forth between it. You don't want to camp to much in free for all because everyone will start going back to you which will lure everyone to come to you and it is a real pain. The next thin you will need is a silencer on your weapon and assassin pro, although assassin works just fine this way you won't show up on the radar from shooting or if anyone calls in a UAV and for those people who have the portable radar.