My clients are always asking on the best positions to have when sleeping to avoid neck and back pain.
Although neck and back pain can be caused by a large number of reasons for simplicity lets explore the most common mechanical reasons for this type of pain. Just as low back pain can be caused by misalignment of joints in the spine the same can be said for neck pain. Often people believe that their low back pain has nothing to do with their neck pain and viceversa. But because of the close relationship of the vertebrae in the neck to working in reciprocity with the vertebrae of the spine in the low back these two types of pains are almost always related to one another. This is largely due to the Lovett Brother relationship of the top vertebrae to the ones in the lumbar spine or low back.
Basically when you turn your head to the right the movement of the top vertebrae will be mimicked below in the last 3 lumbar vertebrae. This is one of the reasons why sleeping in your stomach will be very harmful for your spinal health, unless your mattress has a hole for you to put your head thru. Of course this not being the case as you sleep on your tummy your head will be turned to one side creating torsion in your neck for 1 to 7 hours plus and at the same time this torsion will be reproduced in your low back. This can create a dull low back pain in the morning. It can also create misalignments in the spine that if left untreated can turn into fixated joints that can degenerate with time and cause pain.
Tip 1: Due to the above explanation avoid tummy sleeping and if you do limit this to a very short time until you find your comfortable position
Tip 2: If sleeping on your side try to avoid having a pillow that will raise your head above the line of your spine. Your spine should be aligned with your neck as the image here shows. 
Tip 3: If sleeping on your side and if you are currently suffering from pelvis or low back pain, try to use a small pillow in between your knees.
Tip 4: if sleeping on your back use a small pillow that can be easily tucked under your neck, I personally recommend a Japanese style pillow. These type of pillows are designed to preserve the vital neck curve in your spine. Without this essential curve in your neck, your spine will with time degenerate and cause neck pains. This can eventually lead to disc herniations and early onset of arthritis in your neck vertebrae.
With this position you will benefit from tractioning your neck thru the night passively and restoring your essential neck lordosis. Also if you snore this will allow better airway passage of air thru your larynx thus avoiding possible snoring noises and a more deep sleep. Remember also to lift your chin as you sleep on your side the rule of thumb is that the closer your chin is to your chest while sleeping the bigger the chances will be that you will wake up with neck pain and in time cause degeneration on your spine.
Tip 5: make sure you mattress is not older than 8 to 10 years even the most expensive mattresses carry a 10 years warranty. Remember that unless your mattress is 100% memory foam your mattress may contain coils that with time lose their shape, stability and pliability. I always recommend a mattress that has a combination of memory foam with individually wrapped coils and the more coils the better the quality of the mattress. These range from 800 coils to in excess of 3200 coils. Also keep in mind the breathability factor of certain types of materials and foams as these will affect the temperature of the mattress at night.
The last thing to mention is that it is important that you keep good spinal health by getting your spine regularly checked for subluxations or misalignments by your Chiropractor. The same way you care for your teeth by brushing them why would you neglect your spine by never getting it check? Remember the goal of Chiropractic care if for your body to better cope to stresses so as to when these happen being emotional, chemical or physical by poor posture or sleeping habits your body has a better chance of coping with these better.
