I've never been a big fan of the "everything on random" playlists -- I've got too many long tracks that potentially break up the flow. And since I feel like I'm cheating a song if I hit the next button, I've come up with a way to deliver a good variety without having to linger on a track for long:
Time - is less than - 2:30
Add in a few "genre is not's" to keep the spoken word and other riff raff out and you'll end up with a nice bunch of short-bursty fun.
