Mountain biking requires a different skill set than riding on the road. With practice, anyone can become proficient and have fun.
Climbing: The steeper the climb becomes, the more you want to shift your weight forward, mostly with your torso, to counteract gravity’s tendency to unweight your front wheel. Shift before a major climb so that you do not grind your gears trying to shift in the middle of a steep pitch. Keep your head up, look ahead and be prepared for switchback turns, obstacles or other riders. In loose or slippery conditions, try to stay seated when climbing, to maintain traction.
Descending: Relax!! Breathe deeply and your torso and arms will automatically loosen up. Keep your head up, and look at least 25 feet down the trail. As the trail gets steep, keep your weight back; find a balance between your two wheels so that your weight is evenly distributed, which ensures that both tires have adequate traction. When braking, apply both brakes simultaneously in a smooth manner. If you just want to slightly slow down, try lightly applying your rear brake.
Corners: If you thought careful braking was important on the downhills, corners require even more attention. Slow down your bike adequately before you enter the corner. You should be coasting through the turn, ensuring that your tires and wheels spin freely and have as much traction as possible. If you must brake in a corner, lightly use your rear brake. Keep your eyes up and look through the corner, towards where you want to go. Your pedals should be in the 12 o-clock and 6 o-clock positions, with the outside pedal in the lower position, so that you do not strike your inside pedal on the ground when you lean into the corner. Steer with your hips, pointing them in the direction of the corner. As with downhills (and everything!) it is important to stay loose.
Obstacles: When mountain biking, you can expect to deal with any number of obstacles, including logs, rocks and roots. Riding over these objects requires momentum, which means you cannot slow down too much, just enough to get through the trail safely. Try to approach an obstacle at a perpendicular angle, so that your tires are rolling straight over it. Be aware that if it is wet, objects will likely be more slippery than you expect.
Mud: Some locales are fortunate enough to avoid serious rainfall that results in muddy trails, but most are not. First of all, it should be noted that trails with long, muddy sections should not be ridden because it will damage the soil and scar the trail. However, during a race, you do not have much choice, and when you come upon a short muddy section during a ride, it is okay to give it a try. When you are riding in a muddy section, all of your actions should be more subtle. Accelerations and braking should be smooth and gradual and turns should be initiated through weight shifts rather than steering. Think of it as a challenge to your abilities – have fun with it!