The basis of every bodybuilding technique is resistant exercises. There are several such techniques that help gain rapid muscle mass. All these techniques are used depending on the stamina and weight lifting capacity.
Timed sets involve doing both the concentric (up) and the eccentric (down) phase of the movement over a specified time. The number of times you perform concentric and eccentric movements can be same or different.
In partial reps technique the entire set is purposefully done through a partial range of motion and the focus can either be on concentric or eccentric portion of the partial movement or both.
A giant set usually consists of a number of different set of exercises for one particular body part, done one after the other with minimal break. Giant sets usually involve moderate weights with minimal time gap between two reps.
Forced reps is a process which involves working the muscle group past failure to allow full contraction of the muscles. This technique may require a partner to help you reach your limits. The time lapse between two consecutive sets should be more to get better recovery for next set.
A super set consists of a number of different exercises for two or more body parts one after the other. It is usually done after the main sets. One body part is exercised first, followed by the other. It helps build better coordination between both muscle groups.
Twenty-ones technique involves breaking the motion of an exercise into three effective motions. Then you need to continuously perform 7 reps of each motion followed by the next motion.