Hmm... Of course the "cure" depends a lot on what's causing the problem. A few things that often works for me are:
1. Not using computers, phones, TV or stuff like that for a hour before bedtime.
2. Drinking and eating well during the day, and no sugar or caffeine after 6pm.
3. Taking a walk or going for a run before I go to bed.
4. Reading a book or writing about the day in a notebook just before I go to sleep.
5. Try to exhaust yourself during the day, so your body will need and take every chance to sleep during the night.
6. Clean your room, make your bed, make sure that your sleeping-environment is nice and relaxing.
7. Take a long shower just before bed!I hope that it gets better soon. If it doesn't I would recommend you to contact a doctor!