I have been treating a lot of clients lately with neck related issues. I can't stress enough the importance of having a good pillow as well as the right pillow for the way you sleep.
If you are a side sleeper, you may want to try a high u-shape pillow. This will stop your shoulder from curling and your neck from over stretching on one side.
There are a number of side sleeping pillows available, I recently bought this one and find that I sleep much better. www.the-pillow.com.au
Remember if there are two things you want to spend good money on, they should be your mattress and your pillow.