What to spend money on?
People some times underestimate the importance of buying a good LCD display. Your eyes need a sharp, warm display in front of of them to prevent your eyes from becoming tired, and eventually becoming fuzzy. Sure, having a fast CPU to play those latest games is nice. But don't forget your eyes! That extra 100 bucks could have been spend on a better LCD panel. Although displays become cheaper every week it seems, a good screen still costs a few hundred dollars that some people rather spend on a better CPU or more RAM. Will those 2 items prevent tired eyes, red eyes, dry eyes, or unsharp eyes? No they won't!

Bigger is not better!
Another misconception is that the bigger the screen the better. Not at all. If you see a 19 inch display with high contrast, plenty of custom settings to set it up as you want, and a 22 inch screen with a low contrast ratio and less custom settings, then pick the 19 inch. Your eyes will thank you for it.

FLAT LCD PANEL What you need to know about LCD screens

 

FLAT LCD PANEL What you need to know about LCD screens

 

Different tastes = different opinions
There are many LCD display brands and it can be hard to select the best. If you have been happy with your current screen, look for a new one from the same brand. Big time display brands are Samsung, Philips, Dell, Sharp and a whole bunch more. You may also want to look at AG Neovo if they sell those in your country. The better screens from the latter brand are quite expensive, but the hardware and design is of a higher quality than the more mainstream brands out there. Don't hesitate asking for advice on the well known hardware forums. Do remember that in the end purchase of a LCD screen is a personal choice. Some people speak highly of certain brands' excellent designs, while others feel completely different about that particular brand.