I am not an expert but if you have to do it blind (like most new buyers) you might want to try what I did. I used www.mtbr.com and read reviews to find good components then found a bike with those on it. Probably the two biggest components groups are the shifting and the suspension. You'll need to understand what type of riding you want to do which will determine if you need a full suspension or just suspension on the front.

On component hunting, I read a lot of good things about sram so I wanted a bike them (after trying them, I think they are pretty good). There are a lot of good forks in your price range like rockshox. Just really know how all the components stack up against each other than find a bike the has the most good parts and you like the style for the money.

Happy hunting!

Hal