When seated, keep your back straight and your feet on the ground.
Try to keep your knees and your hips level
If you sit for long periods, you should support your lower back against the back of your chair.
Make sure you get up and move around at regular intervals to alter your body position.
Avoid sitting in hunched position for long period of time such as when using laptop or desk computer.
Relax your shoulders; they should not be rounded or pulled backwards.
Make sure that your back is fully supported. Use a back pillow or other back support if your chair does not have a backrest that can support your lower back's curve.
Avoid looking down at your phone