To get the best numbers on the track, automatic transmissions are brake-torqued.

Meaning they are put in 'D', brakes are engaged using the left foot, put on full throttle and the brakes are released.

Another method is the 'neutral drop' wherein the engine is revved while in 'N' and then the shifter is dropped into 'D'. This is very hard on both transmission and engine and is rarely used nowadays except on junkers.