
Factors that influence your sleep-wake needs include medical conditions, medications, stress, sleep environment, and what you eat and drink.  Perhaps the greatest influence is the exposure to light.  Specialized cells in the retinas of your eyes process light and tell the brain whether it is day or night and can advance or delay our sleep-wake cycle.  Exposure to light can make it difficult to fall asleep and return to sleep when awakened.

The latter portion of this plan is meant to tidy up some of the loose ends, including conditions that can undermine sleep. If the early changes haven't proven to be effective or relevant, it may be because other issues are at play. Ultimately, if your efforts aren't rewarded in the end, it may be useful to speak with a sleep doctor who can provide you the personal assistance you need to overcome any remaining problems. This advice is generally good for all, but carefully crafting it to attend to your individual needs may make it invaluable.
The thalamus acts as a relay for information from the senses to the cerebral cortex (the covering of the brain that interprets and processes information from short- to long-term memory).  During most stages of sleep, the thalamus becomes quiet, letting you tune out the external world.  But during REM sleep, the thalamus is active, sending the cortex images, sounds, and other sensations that fill our dreams. 
A smart tip for jetsetters: Pack melatonin supplements, such as Natrol Melatonin Fast Dissolve Tablets. The supplement helps your body better adjust to the new time zone, allowing you to fall asleep come bedtime and avoid jet lag. But the sleep aid isn’t just for jet lag. You can also pop the tablets when you have occasional sleepiness or when your sleep schedule shifts and you need to get your body into sleep mode. It’s recommended that you start with a small 1 mg dose (take it 20 minutes before bedtime). You can slowly increase your dosage, but don’t exceed 10 mg.
Wear socks to bed. While a cooler core body temperature helps you fall asleep faster and get more restful sleep, cold extremities (hands and feet) can have the opposite effect. If you tend to have cold feet at bedtime, put on a pair of cozy socks, rest your feet on a heating pad, or pile an extra blanket on the foot of your bed. If none of those appeal to you, try wearing a pair of warm slippers in the evening so that your feet will be toasty when you climb in bed for the night.