"My tried and true method:
1. Cold Shower (I read somewhere or have convinced myself that cold is better because the energy it takes your body to warm itself up tires you out) using Johnson & Johnsons Nighttime Bath (the stuff in the purple bottle for cranky babies)
2. Masturbate
3. sleep sleep sleep"
http://ask.metafilter.com/24945/How-do-you-fall-asleep-when-youre-not-tired
or there is always ambien.