Src: http://www.hp.com/ergo/keyprinciples.html
Whether you are an adult sharing a computer at work, or a student sharing a computer at school or at home, each time you sit down, adjust the environment to your needs. Adjust the tilt of your monitor, use a box as a footrest, a blanket on the seat to raise your chair height - whatever you need to adjust into your comfort zone.
Key principles
To promote safety and comfort, follow these principles whenever you use your computer.
Adjust
• Adjust your body position and your work equipment.
• There is no one "right" position. Find your comfort zone, as described in this Guide, and when working at your computer, frequently adjust within this zone.
Move
• Vary your tasks so that you can move around; avoid sitting in one posture all day.
• Perform tasks that require walking.
Relax
• Build positive relationships at work and home. Relax and strive to reduce sources of stress.
• Stay aware of physical tension such as clenching your muscles and shrugging your shoulders.
• Take frequent, short breaks.
Listen
• Listen to your body.
• Pay attention to any tension, discomfort, or pain you may feel, and take immediate action to relieve it.
Remember
• Exercise regularly and maintain general fitness; this will help your body withstand the rigors of sedentary work.
• Respect any medical conditions you may have or other known health factors. Adjust your work habits to accommodate them.