First off the important thing that EVERYONE overlooks with screens these days is the response time. If you intend to use it for gaming its essential that you get a screen with as LOW a response time as possible. My current 2 screens both have response times of 2ms which means flawless gaming. At above 7ms you start to get ghosting when playing games, and this is what ruins the visuals.
Then make sure it has multiple connection points in the back; For example, HDMI, VGA, SCART, and Component. And if possible try to get one with a "proper" configuration menu (ie backlight/gamma/heat/black level etc) rather than the standard contrast/brightness settings that all TV's have.