The best lighting for most people is a combination of overhead fixtures and a desklamp. Keep the overhead lighting dim for computer work to reduce glare (perhaps by removing a few fluorescent lighting tubes). Then turn on the desk lamp when working away from the computer.
If you have a choice of computer monitors, opt for the flattest screen, which is less prone to glare than a more curved monitor.
Another way to cut glare is to tape a piece of cardboard to the top of the computer. It should jut out slightly, shielding the screen from overhead light. Alternatives available in stores include computer hoods and antiglare screens that fit over the front of the monitor.
To reduce glare from a window, place your monitor at right angles to the window.