If it takes you a long time to fall asleep because your mind keeps racing, use what you did earlier in the day to help you focus and drift off more easily.
Leo Babauta on Zen Habits posted this tip as part of an article on becoming an early riser (it's hard to wake up early if it takes you forever to fall asleep):
Close your eyes and get comfortable, then think of the first thing you did that morning - the very first thing, like turning off your alarm. Then think of the next thing, and so on, replaying your morning in as much detail as possible. I never get to mid-morning.
The Most Successful Techniques for Rising Early [Zen Habits]