BioShock 2

This is an easy achievement. Like McBrutalwCheese points out, you can just take a picture of the Splicer walking in front of the window of where you get the camera. It's different than in the first BioShock as this time it's a video camera and, to get the best grade, you want that camera rolling while you're in action and fighting the enemy. The deal this time is that you start rolling the film once you target an enemy with your camera and then you're free to use/change weapons/Plasmids.

Quick tips on filming:

Use combos that work best against the enemy you're fighting (e.g., Electro Bolt a Slicer and then hit it with your drill or using Armor-Piercing Rounds on a Big Daddy will net you an A+).

Change up your research tactics. If you use the same method of killing an enemy, your research points will drop (EVEN if it's an A+ combo). So once you hit that Splicer with the Electro Bolt + Drill combo a few times, Use Incinerate while they're standing in a puddle of fuel or Telekinesis + and explosive canister.

That's really all you need to know and is likely better suited for the 9 research completions achievement in the game, but I figure it's best you know it early and that achievement will come naturally if you follow the above strats.

Good luck and feel free to add your A+ combos versus certain enemies via comments (or compile a list and write your own solution) so our readers can reap the benefits.

Once you get the camera, equip your preferred weapon, then switch to the camera. Find a splicer, and start filming. Kill the splicer. Mix up your weapons and plasmids for a high score. Once the splicer is dead, your film will be graded. The grade decides how much XP you get. Repeat if necessary.