Optimal bedroom temperature is 16 to 19 degrees. If your room's too warm, it may prove hard to sleep - so if you don't like to sleep with a window ajar, open it for a five-minute blast before bedtime. But one of the best ways to encourage sleepiness is to stimulate a temperature drop with a hot bath or shower (or a hot foot bath), an hour and a half before bedtime. The dramatic temperature decline when you get out should make you feel drowsy.