Well first, what you do is take some gasoline or any type of flammable liquid. Then you find yourself one of those Hip-hop kids, the ones with their pants hanging down to their ankles and boxer shorts sticking way out....THEN....you sneak up behind him and slooooowly slide his boxers down until his butt crack is showing. The tricky part is throwing the gasoline on his buttcrack and lighting it so you can watch it smoke. I don't recommend that because lighting someone's butt crack on fire is illegal anyway.
Another method is to light a cigarette and slip the smoking end of it (the filter) right into his butt crack and watch those cheeks flex in and out and puff away!