If your trying to get your headshots up and get a gold weapon for example, the best thing to do is aim high when you shoot at an enemy.

This may not work all the time because the enemy may kill you first.

So get a silencer for when you're behind an enemy and probably get UAV jammer or stopping power.

Stopping power is good for close up combat and will kill the enemy quicker, but the UAV jammer can let you sneak up on the enemy. However your gun may be weaker and it will take a bit longer to kill an enemy and you may get killed.