It depends on what you want it for mate. If you are a grapics designer then you need a wide gamut, wide viewing angles, 20+ inch monitor with either MVA or IPS panels. These are the expensive types. If you are a regular user and can pocket the extra cost you should go for the afforementioned panels also (if you are a gamer prefer an MVA one as it offers faster response times). The IPS panel though is regarded as the best overall. Finally, there are the TN panels, which are the cheappest. TNs are highly rated by gamers though as they are very fast and affordable. They are below their more expensive counterparts in everything else though.
PS: Factors such as contrast ratios, brighntess levels and latency times can be missleading, that's why I did not mention them. For example LG claims an astonishing 3000:1 dynamic contrast for its TN panels. It forgets to mention though that 3000:1 corresponds to around 700:1 static, the measurement that most manufacturers use. Usually, the higher the price the better the monitor. Not always though...