The 1st way to improve your neck posture is to simply be aware of it. For example try to keep your head and back straight vs looking down always or reading constantly with your head down. Analyzing your workstation if you are spending a lot of time on the computer.
Next, do regular stretches and exercises to help improve posture and alignment.These neck exercises will also help with keeping your neck flexible and pain free.
Fourth, see a chiropractor to have your spine checked for misalignments. That could be contributing to your poor posture.
Fifth, Reduce stress- overall stress and feeling down can wear you out mentally but also physically, and most people carry their stress right across their neck and upper back.
Lastly improve your neck posture by using a good neck pillow when you sleep. Most peple sleep with no support at all or often times to much of an incline. Try the neck traction support for the best support.