From WebMD:Slideshow

• The Sleep Cycle: There are two forms of sleep: REM sleep and non-REM sleep. REM stands for rapid eye movement and is associated with dreaming. It accounts for 25% of normal sleep, coming in longer periods toward morning. The rest of our sleep time is spent in NREM, which consists of four stages from light sleep (stage 1) to deep sleep (stage 4). Sleep disorders interfere with normal sleep cycles, preventing a good night's rest.
• How Much Sleep Is Enough?: Sleep needs vary widely from person to person, but general guidelines are:
  • 16 hours for infants
  • 9 hours for teenagers
  • 7-8 hours for adults

Keep in mind that some adults do fine with 5 hours of sleep and others need as many as 10 hours per night.

• Sleep Diary: Charting your habits for 1-2 weeks can provide valuable information. Include:
  • Your bedtime and wake time
  • How long and well you slept (Also add: "How I Felt When I Woke Up)
  • Time awake during the night
  • Caffeine or alcohol consumed and when
  • What/when you ate and drank
  • Emotion or stress
• Exercise in the late afternoon can make it easier to fall and stay asleep – just don't let it get too late.
• A light evening snack of complex carbs and protein can lead to better sleep. Cereal with milk or crackers and cheese fit the bill, but they should be eaten at least an hour before bed.
• Late-night television may be part of your routine, but chances are it is not helping you sleep. Television engages the mind and can increase alertness, keeping you awake. Playing video games before bed or surfing the Internet may have the same effect. The National Sleep Foundation recommends removing televisions and computers from your bedroom altogether.
• You can signal your mind and body that it's time for sleep by creating a bedtime ritual. This may include a warm bath, reading a chapter of a book, or practicing relaxation techniques, such as deep breathing. It's also important to stick to a firm bedtime and wake-up time, even on the weekends.