Exercise during the day. You won't notice the fatigue in your body until you climb into bed, but even a short workout can sap your energy to the point that sleep is inevitable. Note, however, that any exercise should be done in the morning or early afternoon, as late-night workouts will make it even harder to fall asleep.

Get a new bed. It may be expensive, but a fresh mattress could be the ticket you're looking for. It might even be something as simple as an overly-stiff pillow keeping you awake. Barring that, flip and rotate your mattress to avoid uncomfortable craterous indents formed by sleeping in the same spot every night.

The key is to relax the mind, as a stimulated cranium is one that's going to stay awake. Use whatever means necessary at your disposal to do just that and sleep will be but a few blinks away.