If you are getting the right quantity of sleep but the quality is lacking, take a look at your sleeping patterns. You should go to bed and wake up at the same time each day even when you're not working or going to school. Put on your pajamas, brush your teeth, wash your face and perform any other bedtime activities in the same order each night. Eventually your body will start telling itself to wind down during the ritual and you'll be better prepared physically and mentally to go to sleep. It's a good idea to avoid both nicotine and caffeine completely.
Smokers wake more during the night and have more trouble falling back to sleep than non-smokers.
Caffeine, a stimulant, keeps you from falling asleep and prevents deep sleeping. However, if you do have nicotine or caffeine, make sure that it's not close to bedtime. Drinking alcohol right before sleeping also disrupts a good night's rest because it fragments your sleep. Make sure that where you're sleeping is a good environment. The right mattress is very important although there is no one mattress for everyone.