People prefer different sleeping positions. Back sleepers, stomach sleepers and side sleepers all need different pillows to keep their head properly supported and the neck correctly aligned. Without the right pillow, you will wake up with a stiff neck. Stomach and back sleepers require flatter pillows than those who sleep on their sides, so look for a thick pillow to hold up your neck. If you have to sleep with a hand under your pillow to support it, your pillow is too flat and you need an upgrade.
Choose a firm pillow with a dense filling. This ensures that the pillow continuously supports your head throughout the night. Press down on the pillow in the store to test its thickness. Tim Sams in "ABCs of Pain Relief and Treatment: Advances, Breakthroughs and Choices," recommends a compressed thickness of 4 inches for a side sleeping pillow.
A proper pillow for side sleeping should be contoured to the shape of the head and neck. Neck rolls are used by some to support the neck while the sleeper keeps his head on a regular pillow, but this arrangement can easily move during the night. Choose a contour pillow with a built-in raised portion at the base to support the neck and a lower area for the head. Another option is to use a memory foam pillow that conforms its shape to your head and neck. The shape of the pillow must keep your neck straight throughout the night to prevent pain.
The material the pillow is made from will determine its firmness, but allergies should also be taken into consideration. Dense materials retain the pillow's thickness over time. Feather pillows naturally shape to fit your head, but some find the filling irritating to their allergies. Hypoallergenic options have a polyester gel fiber filling to feel like down without the feathers. Memory foam pillows retain the shape of your head and neck when you are sleeping on your side to provide support. Look for a five-pound memory foam pillow.