How to choose a mountain bike depends on what you are going to do with it, if all you want your new mountain bike for is going for a nice leisurely ride on the canal path or a ride in the woods with the dog, well you wont need a full suspension downhill machine with 4 inch travel on the forks and a fully articulated rear end with damping and rebound control.
Where to Start From.
If you do want to go for an easy ride in the park you dont need to spend too much, if you think you will do any off-road riding then big tread tires maybe all you need, but if you think you might try some rough stuff then you will need suspension. Gears will probably be Shimano, brakes must be V-brakes, but could be made by a few different manufacturers, all the rest of the MTB components will depend on how much you can spend. If you go to your local bike shop or big sports store and see what theyve got to offer, then buy it or have look on the Internet and maybe youll find the same thing at a better price.
The Next Step Up.
So maybe you want to be a bit more adventurous, more off-road, more forest tracks and dry boulder river beds, then youll need something a little...