+1 for melatonin. Here is what works for me: Take it 3 nights in a row, 1/2 hour before you want to fall asleep, it will reset your body clock. Then the next time you're experiencing insomnia, repeat.

Also, no caffeine after noon. No food after 8pm. Limit alcohol (sugar in the alcohol keeps me up).

Hope these tricks help you as much as they helped me.