You must be able to see what you are doing easily to avoid eye strain & neck pain.Have adequate light.
Experiment with chair height and tilt until you get it the way your body likes.
Be sure to get the height right to prevent too much bend at the wrist & have some support. The arms should hang loose to prevent the shoulder muscles from cramping.
The continual clicking & small,precise motions involved in mouse use are a repetitive action that can be a health hazard.A few basic rules can help-
1)Hold mouse loosely. Use a light touch when you click.
2)Use your whole arm & shoulder to move the mouse not just your wrist.
3)Keep wrist relaxed & neutral not bent.
4)Avoid prolonged postures.Rotate your shoulders,gently shake your hands & fingers.
Human Set Up
Footrests help as cushions if your chair is not providing adequate support.
Look away from the screen occasionally. Blinking moistens the eyes to prevent burning from dryness.
Do neck stretches,wrist wiggles & leg stretches before login
At least once an hour,get right up off your seat & walk around, stretch,yawn,get the blood flowing & stimulate the joints.