Melatonin triggers sleep -- so it can help you fall asleep sooner, although it will not necessarily help you sleep longer. Generally speaking, melatonin should be taken a half-hour to an hour before bedtime to help you fall asleep (a liquid may work a bit faster than a pill). Although a range of doses have been used in successful clinical trials, keep in mind that melatonin is a hormone -- it may be wise to first see if a low dose works for you. For more about melatonin dosage and cautions, as well as our quality tests and comparisons of melatonin supplements, see the Melatonin Supplements Review >>
For more information about supplements for sleep, see our product review of Valerian Supplements -- which may have a calming effect; our information about L-tryptophan -- which can increase sleepiness and is used by the body to produce melatonin; and a question we answered about L-theanine, which may, interestingly, enhance the quality of sleep and improve alertness during the day.