Get plenty of exercise during the day. Studies have shown that people who are physically active sleep better than those who are sedentary. The more energy you expend during the day, the sleepier you will feel at bedtime. Just be sure not to engage in vigorous exercise too close to bedtime as that can make it more difficult to fall asleep.
Reduce your intake of caffeine, particularly in the evening.
Avoid stimulants like caffeine and limit alcohol. Both, even when consumed early in the day, can affect sleep.