How to Become an Early Riser: "The optimal solution for me has been to combine both approaches. It's very simple, and many early risers do this without even thinking about it, but it was a mental breakthrough for me nonetheless. The solution was to go to bed when I'm sleepy (and only when I'm sleepy) and get up with an alarm clock at a fixed time (7 days per week). So I always get up at the same time (in my case 5am), but I go to bed at different times every night."
Interesting stuff, as I've been consciously trying to start my day ealier lately to positive effect. I've always been a sporadic sleeper, but as Steve says, "...after a while I couldn?t ignore the high correlation between success and rising early, even in my own life."