1) I found that when I reduced my caffeine intake a while ago, I slept more deeply and felt refreshed in the mornings, something which never used to happen.

2) As mikeyman said, a hormone called tryptophan causes sleepiness. Turkey contains a high concentration of tryptophan, and it's why some people feel lethargic after consuming turkey.

3) Also, I've found listening to relaxing music helps. Stick a bit of Debussy's Clair de Lune on the stereo, and you'll be asleep in no time.

4) Oh, and good sex before bed is guaranteed to make you sleep peacefully. That might be worth a try too!