Sleeping problems can be a real hazard, not just by making your whole day pretty miserable, but also to your health.
Try to develop a regular sleep schedule, I don't know what you have going on, but ideally you would go to bed and wake up the same time each day.
Do some kind of regular exercise. You don't have to go to the gym or run miles, but set aside 30 min during the day and jog, pushups, situps, anything like this.
Other health things like eating proper meals and not drinking caffeine close to bed time. Most people don't know but in healthy adults, caffeine's half-life is approximately 4.9 hours! If you can't go to bed at midnight surely you didn't happen to have a big gulp at 8pm did you :)
It probably goes without saying, but make sure where you're sleeping is a dark and quiet place, or at least as much so as possible.
There are over the counter supplements that can be a sleep aid. You can try melatonin. Your body has a natural sleep/wake cycle built into it. Melatonin is naturally produced in your body and helps trigger the sleep cycle. There are no side effects, and it's impossible to overdose; and it will not force you to sleep. Be sure to look on the bottle too, and don't get the one with B-vitamins added in, which nudge you awake.
Finally if you wake up and can't seem to go back to sleep don't lie there and fight it. If you've determiend you can't fall back asleep go ahead and sit up -- have something by your bed you can do, such as a crossword, sodoku, some light reading, etc. Eventually you'll start to dose off again and then you can try to sleep.
Hope this helps.