Although alcohol can make you feel drowsy and may actually put you to sleep, it has the unpleasant side effect of waking you up later on in the night with a headache, stomachache, or full bladder. In addition, once alcohol's sedative effect wears off, there's a rebound effect that actually makes you more likely to have trouble falling back to sleep.
Caffeine, on the other hand, stimulates your brain. Limit your coffee intake to two cups a day. Starting at noon, consume no foods or beverages that contain caffeine.