The bodybuilding system I use is one recommended by Tom Platz. His system is one of ramping for three weeks and then easing off for 3 weeks. Ramping up causes the body to become confuse with all this stress it's being put under, then ease off to give your muscles time to catch up (adapt), e.g.
Week 1
All exercises done at 3 sets, training Endurance 12-15 reps Monday-
Tuesday, Strength 8-10 reps Wednesday-Thursday, and Power
Friday-Saturday.
Week2
Do 4 sets emphasising on Power, Strength and endurance.
Week 3
Do 5 sets again emphasising on endurance, power and strength.
Weeks 4, 5 and 6
Then for the next 3 weeks ease off back to 3sets to give time for your
muscles to catch up, the gains you get after each cycle are mind
blowing.