The 3 x 8 (3 sets of 8 reps) protocol is used for all body parts except for calves, which need higher reps and sets (you can start calves at 3 x 10 or 3 x 12, and then progressively work to 3 x 20 reps).
With this workout the whole body is done every day, so you pick one exercise per body part (for example, neck press for chest, sissy squats for legs, etc.). It does not matter that much if you do this as a circuit (one set of each exercise done successively and then repeated until you have done each body part three times) or all sets at one time (finish all three sets for each body part before moving to the next exercise).
Each body part can be worked twice a week. Vince stressed the importance of a 72-hour recovery stage for each of the muscle groups.
When doing this routine it’s important to remember that Vince stressed intensity first and foremost. Remember, it is not how much work you do, but how much work you do in a given amount of time. Intensity is paramount and is more important than your set and rep scheme.
As for rest between sets, most beginners cannot start out resting only 15 seconds between sets, so Vince recommended 30 to 40 seconds between sets for them. Ideally, you work toward 15 seconds. Remember to hyperventilate between sets to oxygenate the muscles (hyperventilating is deep breathing through the mouth). Conduct the hyperventilating while counting between sets (30 seconds/30 breaths).
Please remember: You can’t do everything at once, you must build up in steps.