Chamomile and a book works every time.
If I have to be certain to get to sleep and am not sleepy, I've taken 1/4 to 1/2 of one pill of my wife's Lunesta, as it's the only sleeping pill I've tried that didn't leave me groggy in the morning. But it is wickedly powerful. I think a whole pill would knock out a rhino. It leaves a metallic taste in the mouth the morning after, otherwise works well.
Any sleeping pills that take over your natural sleep reflex, or circadian rhythms will disable your ability to get to sleep on your own, so I only take something when I feel I have to, like working early or when stressed. They can be very addictive, from what I've seen.