I've lived with spouts of insomnia all my life. And for me, my body may be tired, but my mind decides it still wants to fire on all cylinders. My problem is I think a lot, all the time.
I've tried many things, sleeping aids work, for like 2 hours. (Gave up on them)
But what I've found that works for me is ambient music, and reading. Music with no lyrics, or complex melodies, or just some of those nature tracks, like rain or the ocean. Combine that with a good book and your mind will tend to calm itself.
Oh yes, and a nice hot bath or shower before you lie down has helped me as well.