1.LEARN THE MAPS!
Most of the kills you are going to get will not be because you outduelled the others, but because of your knowledge of the maps.
Which lanes to run, which cover you can use, ... . Use the walls. With that i mean limit the ways people can shoot at you. Standing in the middle of the nightclub,
running across outposts leaves you wide open from all directions. You'll only be providing easy kills for the rest of us.
2.Play goldeneye mode . At the very least you gonna get some experience by hacking a console once every while.