I've dealt with this for a long time.
1. avoid caffeine
2. use your bed only for sleep or intimacy. don't just lounge in your bed; I even recommend getting rid of the t.v. in your room if you have one.
3. avoid sunlight prior to bedtime
4. make sure you aren't in the least bit hungry prior to bedtime
5. have a "white" noise. something low and continuous. like a fan