A lot of your desicion making will really come down to personal choice as there are so many manufacturers and models to choose from but you can start to trim down your list by thinking about and researching the following;
First, knowing what resolution you want use and then know that the monitor you buy is capable of this resolution.
Second, do some online research (newegg, amazon, tigerdirect...walmart even!) for pricing, specs and read reviews from buyers. You'll learn a lot about what to avoid and what sound good to you.
Third, go shopping. Take a look at monitors in stores and ask to see them in different resolutions. You will see that cheaper monitors distort more when using non-native settings that a more expensive model, especially if you choose a 'widescreen' model. Look at the colors and don't be afraid to adjust them yourself.
One other aspect that you might want to consider before spending your money on a monitor upgrade, is your current configuration. Although it is more than capable of covering your present needs, its not really tailored to todays technology nor current media standards. This presents a whole new question which I won't go into here but I think it's only right to bring this up at this point before you spend money in an area that perhaps is better spent on other hardware. Your call though.
