Finally a serious answer:

Double clutching:

1. You're in 6th doing 3,000RPM @ 60MPH and some Mustang is on your ass
2. Clutch in, move shifter to N
3. Clutch out, rev to high heaven
4. Clutch in, shifter to 4
5. Let out clutch when RPMs match your 4th gear speed at like 59MPH

(yeah if you do it correctly you'll barely lose any speed)

Although, I must admit, more often times than not I'll:

1. Clutch in
2. Move shifter to my lower gear
3. During the moving of the shifter I throw it a little gas (the engine and transmission are disconnected -- this is not 'burning the clutch')
4. Pop it in gear and hopfully match my RPMs