If you wake up with neck pain or stiffness, and perhaps shoulder pain too, then it could be because your pillow is not properly supporting your head and neck. Your neck should remain in line with your head as you sleep.
Many sleep experts recommend that you change your pillow every one to two years as all pillows deflate and become less supportive over time. Different fillings do have different durability however, natural down and feather pillows last longer than polyester filled pillows for example.
Sleep on your side or your back for neck comfort not your stomach - sleeping on your stomach can be hard on your spine, because your back will be arched and your neck turned to the side.
Make sure your pillow is higher under your neck than your head to keep your spine straight when you sleep on your side.
Avoid too high or too firm pillows - your neck will be extended which could give you morning pain and stiffness.
You should only need to sleep with one pillow - if you find you need more support then you either have the wrong pillow or your pillow has deflated due to age and it’s time to buy a new one.
Feather and down pillows offer good neck contouring - they conform to the shape of your neck.
Memory-foam pillows can also contour to your head and neck. Their manufacturers claim they help foster proper spinal alignment. They aren’t washable however.
When you travel, use a horseshoe-shaped pillow to support your neck and stop your head drooping - inflatable ones can be handy.