The answer depends on how you sleep. The proper pillow for your sleep position can prevent neck pain and even improve the quality of your rest.
Do you sleep on your side or on your back?
Leg Bed Frame
If you're a side sleeper, the height of the pillow is important. Your head should not be inclined at an angle but instead should be aligned with the rest of your body, like your head is when you are standing up. If the pillow is too flat, your head will be tilted down and if it's too fluffy, it will be tilted up. Either can make you wake up with a kink in your neck.
If you mostly sleep on your back, then you want to make sure to provide support for your neck and the best pillow for that is a contour one. It will cradle the curvature of your spine so that your head is aligned with the rest of your body. When your neck is not supported, your muscles will continue to work throughout the night instead of resting and you may wake up feeling tired and achy. The contour pillows have a thin side and a thick side. When sleeping on your back, it may be more advantageous to use the thick side however, if you have a slighter body frame, the thinner type may be the best for you.
You'll notice that I haven't talked about stomach sleepers yet. From a chiropractic perspective, this is the least desirable way to sleep because it forces you to turn your head to one side or the other for a long period of time. That said the best pillow for sleeping on your stomach, is actually no pillow at all! If you must have one, then get the flattest pillow you can find.
Choosing the right pillow will help you feel more rested and may decrease any neck stiffness or pain you may have. Sleep tight!