I think the best thing to do is to keep a regular schedule by sleeping and waking up at the same time everyday. Ensure that you also eat right throughout the day without skipping any meal and get regular exercise. For more information, check at www.helpguide.org/life/sleep_tips.htm.
WHile laying in bed, practice controlling your breathing... take deep, long breaths. and try to "clear" your mind. as you are laying there keep breathing slowly and deeply. this will slow your heart rate down and relax your mind/body.