So far the best place I have found for this achievement is early on in the game. When you get to The Sinclair Deluxe Tenements and you walk around the Diner, (it is on the map,) there is a body in the corner that a little sister can harvest. The body is positioned behind a news stand (or something of a similar nature,) but point being that there are only two paths to get to her. There is an ammo vender right next to the diner that sells trap rivets. Set them up on the floors and walls in a well spaced apart proximity. Now if you have enough (around 30 or so) you really shouldn't have to worry bout the little sister, so now you have to worry about yourself. The best way to do this is to put her down and run into the diner and get in a corner. With your back to the wall, make sure you can see any splicer that can run through the door so you can zap them on the way in. Pay special attention to the leadheads as one bullet and game over. Using the machinegun helps b/c of the fast rate of fire and the amount of ammo. If you have the special ammo for it all the better. Just make sure whatever you do you use a long range weapon as the drill makes it easy for them to lay a random hit on you. If you have the cash to buy a ton of trap rivets, buy some more after you lay down the ones for the sister and set up your defenses around your position too.
Once the sister is just about done run out there and pick her up.
Another add. In Dionysus Park. Another fantastic spot to make an easy attempt on this. There is a section on the map thats blocked off by ice, IMAGO FINE ARTS. In this area there are several security cameras and turrets. The body is in the back of this room and there is only one entrance. Hack all the cameras and turrets, blue lines if you can, it'll help, and for good measure throw down some turrets. Since this is later in the game, you have access to more stuff, ie cyclone trap, rivet traps, speargun trap wires, turrets, proximity mines, lay these things out to your hearts content. Now for your part, there is a room you can retreat to behind the body. Head back there, and just for added security put some traps around the doors, sometimes splicers will get through here and pester you or head to the sister through the back of your defenses. After that just use common sense, freeze or electrocute people to keep them from hitting you and save beforehand incase you screw up. Just remember you need incinerate on you to get into this area, it is blocked off by ice.