T Nation

What should I look for in a mountain bike?

Hey guys, I’m in the market for a new mountain bike due to the great sales in the bay area right now and the fact that my bike has been ridden into the ground by me. 95% of the time, I’m going to use this bike as a commuter for me to get to/from work (5-6 mile round trip). But the other 5% of the time, I would like to be able to go out and hit some trails on the weekends. Nothing crazy, just to get in some good exercise and away from the gym for a day. What should I look for? What should I avoid? Any good web sites w/ tips? Thanks!