Hot shower right before you sleep.
Sleeping EARLIER (there's apparently such a thing as being OVERTIRED)
Some people use half a dose of melatonin supplement--they say it lets you fall asleep when you want to rather than forcing you to, but there's some increased risk of depression on it.
Tylenol PM? But trust me, you want take it within 30 minutes of planning to go to sleep. It'll do some way trippy things to you if you end up staying awake for 2-3 hours past taking it.