I tell you what worked for me, first masturbate or have sex right before you hit the sack, I think it must release some hormones or some shyt as I feel sleepy after. Second, and this a bit of mental discipline, dont even think about going to sleep, just see laying in bed as something relaxing, reading a book, is good. I found the more I worried about not getting sleep,.thinking I needed a certain amount meant I didn't go to sleep at all. Remember that political leaders have ran countries on 4 hours sleep a night for years, mrs thatcher was one, I think president obama only gets 5-6 hours a night.
Doing this, not seeing going to bed as associated with sleep, cured me of my imsomnia. Try not to use sleeping pills, or get anything prescribed by a doctor,unless it starts to affect your work and your job is threatened or you get serious relationship problems . Because doing that will bite you in the future, you may get dependent on whatever medicine it is and then you are really fukked . Or don't either do what my dad did and self medicate with whiskey at night because he couldn't sleep due to having a stressful job . Gave him a drinking problem.
Also, try and work out what is exactly causing you to lose sleep and if you can sort it out.