there's no trick to it. just put the clippers against skin, lift a little, and clip. the second step is obviously the most important. not only do you want to avoid taking a chunk of skin, but since the clippers are probably used to also serve their primary function you wouldn't want to get any of the bacteria/fungus/etc from your hands/feet into a cut. i find it's easier/safer to do by feel and not use a mirror. and i only do this on the face- i use a razor for the neck.