You could also try meditation. It helps one to find a way to turn off the brain when it is not needed.
I'm not an active practitioner of meditation, but I've been using some light mindful exercises [1] when going to bed, and it helped me falling asleep faster. It used to take me 30-45 minutes to shut down my brain; now I can do in 5-10.
Melatonin also helps, particularly when it's getting late and I'm too excited to sleep. I only take 300mcg, which is enough to make me want to sleep. But I use only as a last resort. It sometimes causes very vivid (and infrequently even lucid) dreams, and then my brain doesn't rest as much, and I wake up tired next morning.
[1] Nothing too fancy; just some tips from "Search Inside Yourself" [2]. Basically control your thoughts, empty your brain, focus on breathing, and consciously think on every muscle of your body. Rinse and repeat.