Native res is important. LCDs scale the image if you use a lower res than native. This means that if you play games and want to reduce resolution to improve frame rates, you will suffer some noticable blurring.
Response time is imporatant if you dont want ghosting in games or video. The figures are quoted in different ways though so be carefull. Anything quoted at 16ms or less should be ok for games.
Contrast ratio is important if you want to watch videos/TV shows, as black level can be a bit 'grey'. This isnt so much an issue in games really.
Colour reproduction - I forget all the technical terms, but I know some LCDs, especially those with low (good) response times can have a lower colour fidelity, which you may or may not notice.
Very brief but I hope some of that helps.