When sleeping on your back, place a soft pillow under your head and shoulders, a rolled-up towel under your neck, and a pillow under your knees to support all three spinal curves.
When sleeping or lying on your side, place a pillow under your head to support your neck and to keep your head level with the rest of your spine. Place a small pillow between your knees, keep your knees bent, and square your hips so they are perpendicular to the mattress - this eliminates any unnecessary stress on your spine.