Giant sets are a great training technique and will really test your endurance and strength. They involve the combination of several exercises for a single muscle group all performed in quick succession. The exercises should be staggered down from the most difficult to the easiest. As the exercise intensity decreases the number of reps increases.
Lets us look at giant sets for shoulders as our example: Select 3 exercises as a general rule of thumb. Standing barbell press is your main builder, then Smith machine presses as a second compound movement and lateral raises as your final exercise. Have the equipment set up prior to your set to minimise time between activity.
Begin with standing barbell. Perform 6 solid reps with good form, then immediately proceed to the smith machine where you complete 12 full reps with consistently good form. As soon as the weight has been set to rest make your way to the dumbbells and perform 24 solid reps with good form. All sets should be taken to or beyond failure, and if a spotter is on hand forced reps could be included to help push the muscles past their currently level of ability.
This style of training is effective due to the continuous load the muscle is under from different angles. By decreasing the intensity of each exercise you can increase the number of repetitions and therefore recruit more muscle fibres.