I suck at sleeping, too. Some things that have worked for me:
1 - If I'm not tired, don't go to bed. Stay up, read, work out, anything. But I don't go to bed until I'm actually tired.
2 - Do physical labor during the day. A good solid workout really helps me out when it comes to sleeping.
3 - Drink more water, less caffeine. It sounds silly, but it works. Even sillier, when I'm on more water, I'm often more alert then when I'm on a pure caffeine diet.
4 - When it's time to go to bed, stop and read for a few minutes. Avoid techno-thrillers, horror novels, and the like. Pick something calming and slow. The classic example is the Navy's Nuclear Reactor Plant Manual -- chapter 24 of Volume 5, on the maintenance and repair requirements for small nuclear valves is a favorite of mine.
Good luck, and relax.
