Reduce or eliminate caffeine and nicotine intake.
Caffeine and nicotine are stimulants that can stay in the body for hours. Sensitivity to the effects of caffeine can last as long as 8 to 14 hours. There is no "normal" amount of caffeine that can be consumed without affecting sleep. The best practice for caffeine consumers is to limit caffeine consumption as much as possible and to avoid drinking caffeine close to nighttime.
If you are experiencing disturbed sleep, it's best to eliminate caffeine consumption for a period of 6 to 10 weeks. If the sleep issues continue, then seek medical advice.
Many view the act of smoking a cigarette as a relaxing practice, however the nicotine inhaled actually "revs up" the body and can reduce the efficiency of sleep.