Taking drugs to help sleep usually interferes with the sleep stages. Sleep from tranquilizers(benzos), or alcohol is very unhealthy sleep and does you no good.
Some people take supplements like melatonin or 5htp. For me these supplements only made things worse. I find that drinking a tall glass of milk about an hour before bed makes me really sleepy. Also a little bit of mild excersise a couple of hours before bed seems to get the serotonin lifted a bit.
My doctor told me you always want to sleep in an extremely dark room with no tv on. Ive read that the conversion of serotonin to melatonin occurs when we are in the dark. Apparently thats the reason why people use light therapy for depression. Staying in the light may help correct an imbalance of serotonin/melatonin.