Sunlight through a window or a lamp that is shinning directly into the eyes of a person sitting at the computer are examples of direct glare. Sunlight or a light shinning into the computer screen and reflecting back to the person is indirect light. A monitor should never be placed by a window with the user either facing or with their back to the window. In either case, the light from the outside will directly or indirectly reflect in the screen. A computer may be placed at right angles to the window, or better yet, at the other end of the room as far away from the window as possible, thus avoiding any kind of glare from the outside.
Overhead lights can also cause glare problems.
If possible, the overhead lights should be dimmed so that the amount of light from the overhead fixtures is about equal to the light from the monitor. This can be better controlled if task lighting is used as much as possible. If dimming lights or task lighting in the room is not possible, a tent placed on top of the monitor can do wonders to remove a lot of the overhead glare. This tent may be of cardboard or other stiff paper and taped to the top of the monitor in such a way that all white spots and other glare is removed from the screen. If a tent is used to control the glare, it is very important to ensure that none of the vents in the monitor are blocked.