I love claymores I have 300 something kills with them so far and that number is only going to rise.
I love to go to popular spots on maps and set one down and then keep it moving, I always get kills from it because there are certain parts on every map people just always go to.
I will also run down one side of a map, set one down then run back to the other side, another easy way to get a kill from them.
There great in Domination ( even more so when your on a garbage team ) I will set one down on one side of the point I am trying to capture and then watch the other side so it has my back so to speak.
The real trick is learning to put them in spots that will get you kills but were people would never expect one, those kills just make me smile everytime.