Melatonin works for me only if I have not taken it in a while. Two nights in a row and it gives me a very unrestful sleep with lots of circular dreams. I have had much better luck with valerian root. Valerian can also can be used during the day.
WARNING: Valerian has some abuse potential at least for me. I was using it mellow out anxiety attacks that were induced by drinking, in very real sense I was using to facilitate drinking. Oh and it smells like puke.