I don't know...I don't think you can just pick one thing and perfect it and grow. I think it's obvious that it's a combination of all the things you do. If you do curls, kickbacks, and use the pec-deck everyday, you're probably not gonna grow much...unless you're eating a shitload, then you'll get fat.
I think when these people come onto the boards asking why they're not growin, the first thing they should be told to do is start doing deadlifts, squats, pull-ups, etc...and also get their diet in check. You start doing those two things, and you'll grow pretty fast. Put them into a good training program, with optimal volume, frequency, and intensity...and you'll well on your way to your goals...no juice necessary.