Patch asked for descending tips in the thread about Robert Hyndman's passing. I didn't feel it was appropriate to discuss there, so here's a new thread.
When we speak of descending on a bicycle, we generally mean "cornering swiftly but safely while descending." My descending tips are pretty simple, but they stem from 15 years of motorcycle riding primarily:
1) On the street, brake before the turn, set a safe entry speed, and enter the turn off the brakes (on a motorcycle, you'd have a bit of maintenance throttle to set the suspension, but on a bicycle, gravity's your only engine here). Come off your brakes gently so you don't get a sudden rush of speed from gravity just as you enter the corner (this is typically not dangerous, but it scares people).
2) Make sure you have assessed the appropriate line for the corner (and the subsequent one, if you can see it). Enter the corner 12"-16" from the outside, apex 12-16" from the inside, and exit 12"-16" from the outside, to give yourself room from oncoming traffic and gravel or other debris at the apex.
3) Trust your tires. If you've come in too hot, remember that your bike can lean over further than you think possible, easily 45 degrees. Breathe out sharply, stay loose, and push on the inside handlebar, and you'll generally make it.
4) For corners where the apex and/or exit are obscured (common in the mountains), slow to a point where you could reasonably negotiate most unseen obstacles in the corner. (Common sense would say 100%, but cornering at rates where you could stop 100% of the time for a flock of sheep or parked tractor insn't always practicable.)
Proficient Motorcycling by David Hough is a good book on motorcycle dynamics and cornering. Much of it applies to cycling on descents as well.