20 rep squats, and GOMAD (Gallon Of Milk A Day) was the old school ticket to building big muscle fast.
Just don't increase the weight too fast. Really it should be increased incrementally, work the hell out of the weight you are using, before you increase the weight. For natural bodybuilding you don't have to do much more than lifting your body weight for results, as the body will only produce so much GH at a time, and lifting heavier won't help.
If you are training for power lifting, then it's a whole different kind of training.