Avoid stimulants such as caffeine and sugar for several hours before bedtime. Do not exercise or be very physically active for an hour or two before turning in, Reading is better for getting sleepy than TV or going on line. If you want a bedtime snack, pick one with carbs but not sugar. A low-sugar cereal with milk is good.
Avoid drinking caffein drinks and eating sugar for several hours before bedtime can sometimes help. Find something relaxing to read or a show to watch about 30 minutes before going to bed so you aren't as active and begin to kind of relax before you actually go to bed for the night.