A lot of the musculoskeletal issues people have come from bad posture. If you keep an eye on your posture and try even a little bit to have good posture, you will see an improvement in neck, back pain and sciatica.
A great tip is to keep your ears aligned with your shoulder. So when you sit or walk, if you are hunching forward, consciously move your head back and align your ears with your shoulders.
You can also do the same when you are sleeping at nights on the side. If you find that your head is too forward, bring it back and align it with your shoulders. After a while this will become natural and a habit of aligning yourself will form.
You will see a difference within a few weeks and start feeling better even if a little at first. Bad posture is recipe for disaster later in life so pay attention to your posture ASAP.