Of course every body is different but here is a general rule of thumb when it comes to your sleeping position and effects on your health. For specific guidelines regarding your proper sleep posture please ask your chiropractor at your next visit.
Please note that sleeping on your back and side ( especially left side) are most beneficial for your health. Not mentioned in the picture but side sleeping also has been shown to be best for brain health as this is the position where the body can release toxins from the brain area.
In both the back and side posture positions please be sure to make sure your spine is in a straight line as much as possible. This includes your neck when using a pillow. For back sleepers a pillow underneath your knees helps to reduce stress on the low back. If you are a side sleeper a pillow between your knees is also a good idea to help relax the low back and hip area.
Again please be sure to speak to your chiropractor for what is best for your specifically.
(Image used with permission from Purple)