Do you exercise? Wearing yourself out completely, physically may help. No caffeine, no naps. Calcium and Magnesium help. Turn the lights right down at night so there's really just enough light to see. Turn off the telly. Try meditating. When trying to fall asleep focus on your breathing and nothing else. Try tensing and relaxing every muscle in your body. Go to bed and wake up at the same time every day, even weekends.
Oh actually, a good technique that was told to me is to go through the alphabet and name two girls or boys names (sometimes I've done boys and girls!) for each letter. I thought it would be too stimulating because you actually have to think about it, but suprisingly it puts you to sleep!