Sleep hygiene is the term used for methods and habits used to ensure a good night's sleep. Various guidelines exist, created by sleep centers, medical hospitals, and other medical and mental health professionals. These guidelines include eating and exercise habits, understanding the circadian rhythm, and understand sleep's role in our lives. The University of Maryland Medical Center is a highly cited source for sleep hygiene guidelines.
One of the most important habits is to go to bed and get up at the same time each night and morning. For example, go to bed each night at 9pm and get up each morning at 5am. This helps your body and mind to establish a habit and to set your circadian rhythm. If you find you wake up earlier than you thought you should, adjust the time you go to sleep. For example, if you go to bed at 9pm and awaken refreshed at 4am, go to bed at 10pm. Some people do not need a full 8 hours. You may find you need more than eight and, again, adjust the time you go to bed. Also be aware of your 'chronotype': night owl or morning lark.
Another habit is to not use the bed for anything other than sexual relations and sleep. Do not read, watch television, or eat while in bed. This is another way to get your mind and body into the habit of going to sleep when you lay down.
National Sleep Foundation - 
Harvard Medical School - 
1. chronotype - http://en.wikipedia.org/wiki/Chronotype