Easiest to achieve on Level 1 - If done correctly you can earn 360 achievement points in one level:
At the beginning of the level, briefly follow a soldier a soldier past a checkpoint. On the left hand side is a door. Go through the door up the stairs and just before you see a soldier sitting in a chair you can
change into your first disguise - a soldiers uniform. This allows you to roam around freely in part of the level.
Go to your first assassination target. You will see your target in a room working on a 'patient'
before you enter the room tere is an electric Generator on the back wall. Switch this off and wait for your target to leave the room, while he is away run into his room and on the far side of the bed
Turn the Switch on - when he comes back he electrocutes himself.
Change into his disguise, hide his body in a wardrobe and head towards your next targetIn your Surgeons Disguise head towards your target.
He will be near a room with a large dining table. Just beyond this is a small medical room.
in the room is a syringe on a small cabinet. Pick this up. Wait for your target to come into this room and after some dialogue he will lie down on the medical bed. Make sure you close the door then
Assassinate him using the syringe. Change into his disguise, pick up the key from his body and hide his corpse. Follow the Map again and head into a room with a large safe, open the safe and burn the video tape. Now head towards the objective and meet the prisoner. The achievement will pop once you leave the area.
Here is a full video guide with all eight achievements. I recommend you follow this.