The basics of good posture
How can I improve my posture when sitting? Many Americans spend a lot of their time sitting - either at work, at school, or at home. It is important to sit properly and take frequent breaks Switch sitting positions often Take brief walks around your office or home Gently stretch your muscles every so often to help relieve muscle tension Don't cross your legs; keep your feet on the floor, with your ankles in front of your knees Make sure that your feet touch the floor, or if that's not possible, use a footrest Relax your shoulders; they should not be rounded or pulled backward Keep your elbows close to your body. They should be bent between 90 and 120 degrees. 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. Make sure that your thighs and hips are supported. You should have a well-padded seat, and your thighs and hips should be parallel to the floor. Source