What I do is try to stay on the outside of the map and sneak around till you get behind someone and jsut aim at the head..

a good way of getting headshots is always aim high....main thing is your K will go down no matter what so dont care about it....dark matter is the hardest camo get but in the long run you can show off a nice piece of skill sooo first thing 1 get good at hardcore i hated hardcore but i then got good and could get my camos alot easier hardcore freeforall is easy for beginners because of no map and everyone is a enemy camp if you have to and shoot high use high caliber it helps alot and for long shots use the vertex 3 and zoom out you can get long shots very easily instead of full map kills for it to count it counts from like 10 feet away i cant help you with getting better but that was my tip and experience that helped me get dark matter

I would say try and put yourself into gunfights. Weird right? No. Put yourself in gunfights and aim at the chest, the view kick will get you, your headshots. That is what I do at least. Also for ARs use High Caliber I think it is called.