Color calibrating your monitor is essential if you want to see accurate color on your computer. I use the Spyder 3 Pro by Datacolor to calibrate my monitor. If you don't need extremely accurate color for making prints or publishing you can adjust your monitor yourself by following these instructions.
Adjust the brightness and contrast until all 17 shades of gray in the bar below are distinct.
The best way to do this is to turn up the contrast all the way to get the brightest white your monitor can display. Next, turn down the brightness to get the blackest black you can while still being able to distinguish the next brighter shade of gray in the bar above. With your contrast and brightness set this way you will not be missing any detail in the shadows or highlights of photographs.
The bar above and the background of this page should show shades of gray. If they look like they have a color cast, adjust your monitor until they do not.