I improved my ergonomics dramatically by doing the following:
1) Evoluent Mouse
2) Ten Keyless keyboard, places the mouse nearer to the keyboard
3) taking 5 minutes breaks(walking away from the computer) every 55mins of work.
Like mkawa said you have to evaluate your current ergo situation, alot of stuff that i think you can google, including:
monitor height and distance from eyes, adjustable chair etc.