But that has changed over the last year. The single most significant improvement has come in the form of a new, well-fitted bike. My first bike was bought off craigslist, generally in my size, but not really. Perhaps I was seated too far forward, too high, or the frame was just not right for me and this led to crashes.. lots of them. The new bike is awesome. I love the fit, the way it feels, and the confidence it inspires. So my first piece of advice for anyone interested in mountain biking is do not buy your first mountain bike off the internet! Test ride several models and spend the extra dollars to buy something that fits. Get fitted by a bike shop. Performance Bike is not a bike shop. It really really matters on the dirt.
But many people will tell you that. Now lets get into some seemingly trivial tips and tricks that really really help. First, unclipping. You really have to master unclipping. And this is not unclipping with sufficient warning or forethought as in road or triathlon, but immediate, sudden, and unexpected unclipping -- imagine riding through a rock garden and your front wheels jams into a rock... unclip and steady yourself; you're riding in some wet stuff and the bike starts to slide... unclip and avoid the fall; you're climbing at 0.002 mph up a 35% grade and you run out of gears or gas... unclip and hold on for dear life! Imagine any of the above scenarios with the inability to unclip -- the result is never going to be good. A fall on rocks, sliding on loose dirt, or falling backwards down the trail with a bike attached is an awful situation and one that I have experienced.
So, practice unclipping religiously. Note that unclipping from mountain bike pedals can be quite unnatural at first. I have eggbeater pedals and came to them from Look road pedals. For the first two months I could not unclip at a moments notice or at certain angles or crank positions. This led to a lot of falls. But I kept at it and now I can unclip at will. You can't imagine how liberating that has been. You can try riding stuff that you previously would have walked. You can try going over a large tree stump knowing that you can put a foot down on top if need be, whereas otherwise you'd be falling sideways several feet to the ground. You become a better, more confident rider. So practice this over and over, perhaps in your back yard or in a grassy field at really really slow speeds. Have your 5 year old shout unclip randomly, make it a game.
The next most important thing is to trust the bike. Granted trusting the bike is not easy. But the bike will clear rocks, roots, and stumps 95% of the time if you keep pedaling (for the other 5%, there is unclipping). In fact, it is arguably easier to send rock gardens with raw power and speed rather than slow nimbleness and precision. But this requires committing to and trusting what the bike can do. 29 inch wheels really roll over most anything, so trust that they will and go for it. Use movements in body weight to help the bike along (i.e. shift back, lift front wheel slightly to clear a stump or large rock, then shift weight a bit forward to let rear wheel through).
What else? Oh yeah, look forward not down at your front wheel. This is so critical. My first several months were spent in a tunnel vision focused on my front wheel. I argued that I can see the rocks and roots better if I focus on them. Not true. Look several feet in front and trust your damn bike. It will clear those roots and your forward vision will help you see the best lines to take. If you have an experienced buddy, I've found it helpful to ride behind them and follow their lines. If your experienced buddy is attractive, focus on his/her butt.
What next? yeah, bike weight... but its not what you're thinking. The single heaviest thing on your bike is you. The angles at which we ascend and descend in mountain biking are much steeper than other bike sports. So where you sit on the bike and how you move your weight around really matters. So use body weight as a counter balance. What does this mean? well this means to unweight the front end for a split second while the front wheel clears a large barrier; this means sliding back on your saddle, even hanging your butt back off the saddle, inches from the rear wheel on very steep descents; this means leaning forward at the hips when climbing steep slopes to keep weight on the front wheel so it doesn't hop around. The consequences of not counter balancing can be devastating. Imagine endo-ing off your bike on a fast descent because you were too far forward. Not fun.
Tire pressure. Low pressure is good but too low and your tires will roll on tight turns and the bike will lose traction. The pressure recommendations on stans no tubes website, for instance, are too low. I followed their advice and crashed numerous times. I talked to my coach and he recommended adding 5 psi and I've have no traction problems. Of course, don't go too high else your tire will bounce around. But keep in mind that there is such a thing as too low tire pressure. I weigh 150lbs and ride 24-26 psi. Previously I was at 19-20 psi and wasn't very happy.
Full suspension or hardtail. My first bike was a hardtail and my new bike is a full sus. I am biased. All else equal, I do not see why anyone would prefer a hardtail over a FS, especially since the newer FS models can be completely locked out to replicate a hardtail, or even a rigid bike. Yes, they are a bit heavier, but only just, and the advantages of rear suspension in technical terrain outweigh the costs. But others may disagree. Hardtails are cheaper though, so there's that. But know this -- a hardtail can go anywhere a FS can, so don't be held back if you prefer a hardtail. My gf and I even saw a fully rigid bike on slickrock -- go figure.
Happy riding (and less crashing)!