i'd also like to recommend that you just use your bedroom for sleeping.
get your computer, TV, etc out of there, leave nothing in there that can distract you from sleeping.
maybe it's just a placebo effect, but this recommendation was made to me, and i got everything out. now, when i even walk into my bedroom during the day, i start yawning.
caffeine and nicotine also effect your sleep patterns. if you're addicted to either one of those, drop them.
i personally have a problem with hypoglocemia while i'm sleeping. i try to have a small snack high in protein before i go to bed, just to keep the bloodsugar levels up. cottage cheese is very good for this because of a slow-digesting protein present in the food.
other than that, sleeping on a schedule will help stabilize your circadian rhythm.