My $0.42:
1. Shifting - whether it is an upshift of a downshift: the movement of the shift lever is a three step process:
- Out of the original gear
- Through the neutral plane
- Into the required gear.
2. Downshifting -- NEVER EVER use a downshift to slow the car down. The proper technique to engage a lower gear is to do a technique commonly referred to as a "heel and toe downshift." If done properly, a heel/toe downshift will not change the decelleration attitude of the car whatsoever. If you want to slow the car down, use the brakes - that is what they are designed for, and replacing worn brake components (pads and rotors) are far cheaper than a tranny rebuild. (Search the DE/Track forum for more details on the heel-toe downshift).
Here's a rough visual idea of the heel/toe downshift is:
The throttle is blipped as the clutch is released in order to rev-match the motor to the lower gear.
-Z