Also see this thread: [The wonderful 5-htp (5-hydroxy-tryptophan) about 5-HTP. It’s good for insomnia too. 5-HTP is a precursor to Serotonin which is a precursor to Melatonin which is released by your pineal gland to tell your body when to sleep. Taking Melatonin also works as some others have mentioned, but 5-HTP lets the body process things into Melatonin more naturally.
I also highly agree with cutting out all kinds of caffeine. It does terrible things to your body’s natural rhythms. Besides that, it also helps to try to keep a regular schedule of sleep, wake, and meal times. The body is better able to keep it’s cycles going if you have a regular schedule. You should try to eat your last meal about 3-4 hours before bed so you don’t go to bed stuffed or hungry.