What is the best way to treat sore muscles (like neck, shoulder and back musles)?

Sore muscles: If there is an acute injury of a muscle, apply cold compresses 20 minutes 4 times daily for 48 hours and then switch to hot(not too hot!) applications. For more chronic soreness I favor heat, followed by rubbing in liniment like BenGay. Taking anti-inflammatory medications like ibuprofen or naproxen relieve pain. Of course avoid overuse of these muscles to prevent soreness. See MD as needed.