Originally Posted by RecceDG

The mountain bike world has really gone extreme into market segmentation; it can be very, very confusing as to what to buy, especially as those market segments frequently overlap or are poorly defined in the first place.

So my first bit of advice is to ignore the marketing category of the bike ("trail bike" vs "All Mountain" vs "Marathon XC" etc) and instead concentrate on the specific technology used on the bike.

Here are the broad strokes:

1. Hardtail vs Full Suspension - hardtails are simpler and usually cheaper (until you start seeing the specialized carbon race hardtails which are very much "horses for courses") Full suspension bikes are FAR more capable and forgiving, but they take a little more maintainence and the variety of different setups can be baffling. They will also be more expensive;

2. 26 vs 29: 29" wheels are better at high-frequency, low-amplitude bumps than 26" wheels (even with suspension) but the bike will be somewhat less manouverable and tires and tubes are harder to find. If you will be riding on fire roads and/or bike paths exclusively (like a rails to trails path) a 29" hardtail will be the way to go. If you want to get into singletrack, the 26" wheel is the better choice;

3. Brakes: Go hydraulic. Mechanical (cable-pull) brakes work, but they take constant tweaking to keep working. It is worth a little extra money to get hydraulic disks;

4. The most important part of the bike is the fork. It is worth spending a little more money to get a good fork than to get a bike with a cheap fork. Air vs coil is a lesser consideration, but rebound damping is a MUST and adjustable compression can be handy.

DG