You can perform supersets in two very different ways and get very different results.
Opposing Muscle Group Supersets
One common form of a superset workout includes working two opposing muscle groups back to back and then repeating the circuit. A common superset includes performing one upper body exercise and immediately move to a lower body exercise. For example, perform one set on the bench press and one set on the leg press. Another easy method to plan supersets is to alternate with opposing muscle groups. You can combine the bench (which works the chest) with the seated row which engages the back.
Supersets of this type are a great way to reduce the time your workout takes. These supersets are very similar to a circuit training routine. Although supersets tend to focus on two exercises at a time, and circuit training routines often have up to ten stations, both workouts require little rest between exercises.
Same Muscle Group Supersets
The second way to perform a superset workout is to choose two different exercises for the same muscle group and perform them back to back without a rest. Performing quadriceps extensions immediately after squats is an example of a this type of superset.