Descending ability, like any other fine-motor skill, is best improved with practice. The more time spent on technical descents the more your confidence and speed will develop. The difficulty for bicyclists is that each descent requires a climb. While there are hot-shots who practice on their motorcycles before races with strategic descents, for most of us the best skill training comes from regular group rides. Group rides are the best path to developing real bike handling skills, whether descending or not.
After experience the second most important component of a fast descent is relaxation. Anxiety does impair concentration and can cause you to miss important aspects of the road surface. Pushing the speed to the point of fear will not develop good descending skills. Work first on relaxation and smoothness (no sudden movements, braking or turning) and speed will follow.
Third in importance is technique. Technique, however, is difficult or impossible to learn from reading about it. For that reason this article touches on just four of the many technical facets of descending: apexing, breaking, lean, and passing.
Apexing is the art of straightening out a corner by using the breadth of the lane or roadway. A fast descender will set up his or her line well in advance of a corner, entering it from the outside edge of the road for the widest possible angle. The apex, or mid-point, is crossed at the opposite or inside edge of the road, finally exiting again on the outside (always leaving room for traffic, error and unforeseen hazard). The key is to _gradually_ get into position and _smoothly_ follow the line through the corner. If you find yourself making _any_ quick, jerky movements take that as a sign that you need to slow down and devote a little more attention further up the road.
Use the brakes ONLY up to the beginning of a corner. NEVER APPLY THE BRAKES THROUGH A CORNER. At that point any traction used for braking will reduce the traction available for cornering. If you do have to brake after entering a curve make every effort to straighten your line before applying the brakes. If the road surface is good use primarily the front brake. If traction is poor switch to the rear brake and begin breaking earlier. In auto racing circles there are two schools of thought on braking technique. One advocates gradually releasing the brakes upon entering the corner. The other advises hard braking right up to the beginning of the curve and abruptly releasing them just before entering the curve. Cyclists should probably combine these techniques depending on the road surface, rim trueness, brake pad hardness, headset wear and the proximity of other riders.
Motorcyclists and bicyclists lean their bikes very differently in a corner. Motorcyclists keep their bikes as upright as possible to accomodate the flat-profile tires and avoid scraping pegs or pipes. Bicyclists on the other hand lean their bikes into the corner and keep the body upright. This makes it easier to transition into and out of corners. Both motorcyclists and bicyclists extend the inside knee down to lower the center of gravity. To _pedal_ through a corner make like a motorcyclist and keep the bike upright while the inside pedal is down.
One of the most difficult aspects of fast descents is passing. Unfortunately, there are good climbers who are slow descenders. As a result it is not always possible to begin a descent ahead of someone who you may want to pass. If you find yourself behind a slow rider either hang out a safe distance behind or pass quickly but carefully. Passing on a descent is always difficult and can be dangerous. By the same token, if you find yourself ahead of someone who obviously wants to pass, let them by at the earliest safe moment. It's never appropriate to impede someone's progress on a training ride whether they are on a bicycle or in a car. Always make plenty of room for anyone trying to pass no matter what the speed limit is.
Keep in mind that downhill racing is not what bicycle racing is all about. There is no need to keep up with the Jones'. This is what causes many a crash. Compete against yourself on the descents. Belgians are notoriously slow descenders due to the consistently rainy conditions there yet some of the best cyclists in the world train on those rainy roads. Don't get caught pushing it on some wet or unfamiliar descent. Be prepared for a car or a patch of dirt or oil around _every_ blind corner no matter how many times you've been on a particular road. Take it easy, relax, exercise your powers of concentration and hammer again when you can turn the pedals.
If you're interested in exploring this further the best books (and videos) on bike handling I've read are the "Twist of The Wrist" series by motorcycle racer Keith Code.
Roger Marquis (www.roble.net/marquis) See also rec.bicycles FAQ 9.14