I've found, for myself, maximum mass gain comes from:
1) 6-8 reps region, until mechanical (i.e., good form) failure
2) MWF gym visits, with my Tuesday/Thursday reserved for good ol'
fashioned cardio
3) High protein intake: I down about 40+g of protein in my meals, when
in a growth phase, plus a good dose of COMPLEX carbs for energy
4) Stay away from Creatine. Seriously. This stuff'll make you big in the
short term, but I don't know anyone who's been able to maintain
significant benefit over a long period of time.
I went from about 275 lbs and a 30% body fat down to 180, 12%, SLOWLY, to avoid any sort of nasty stretch marks, metabolic effects, etc. I'm building a lot of my old strength back (was fat AND an offensive lineman, so I had some lean mass hidden under all my insulation,) but it's been hard. However, arms are lookin' good, and I've got my back strength back up.
Chest is responding slowly, but eh, we all got one area that'll be a bear.