Dropping the clutch, or launching, is a technique used in racing for quick acceleration. The idea is to rev the engine to produce maximum torque, drop the clutch and then apply that power to the wheels, with a minimum amount of spin.
Position your vehicle and come to a complete stop. It's best to perform a launch on a track under the proper conditions.
Push the clutch all the way down with one foot and press the accelerator with your other foot. Raise the engine's RPM to a consistent level, keeping it at a moderate range for your first try. Once you become familiar with the procedure, you can increase the RPM.
Lift your foot from the clutch slowly, to the point where the car is about to start moving, and then keep both pedals steady.
Wait until you're ready to launch. Slowly let up on the clutch, and at the same time quickly press the accelerator to launch your vehicle. You want a quick launch without an extreme amount of tire spinning. If you have too much tire spin, lower the RPM on your next try.