Well, you shouldn't be doing it. And you probably won't enjoy what happens if you get caught doing it.
If you really want to though, and don't want to get caught, here's your best odds. Don't plan it, think of it about 3 minutes in advance, make it someone you don't know in a place where you aren't personally well known, and walk away. Odds are you'll never be questioned, much less caught.
Ask a homicide detective. The murderers they love are the tricky, meticulous planners because they almost always screw up. Its the sudden, possibly random stuff that they have trouble with.
