BioShock 2

After receiving the camera, you want to use it as frequently as possible on every enemy you see. Start the camera, then attack the enemy with an assortment of different attacks. You'll receive a score and letter grade on the left side of the screen after the enemy dies based on how varied the kill was.

Do this on every splicer (and security turret / camera ) you see. You will likely get this achievement on a common early game enemy like the leadhead or thuggish splicer.

This is pretty simple... as soon as you get the camera start filming and killing enemies...
the easiest to max out are the Leadhead Splicer and the Thuggish Splicer as they are the earliest enemies you will meet

Very easy, when you enter paupers drop, you'll be tasked with an objective to find a genetic research camera, whenever you see an enemy, use the weapon selector wheel (RB) and whack it out, the easiest enemy to do this on is the thuggish splicer, i also suggest using a range of plasmids and the shotgun for the fastest way to unlock this.