The thing is that, as I've mentioned, NO products are usually packed with creatine, caffeine, and sometimes other ingredients besides arginine and other things directly designed to stimulate nitric oxide ... Which begs the question of what is really NO, what is placebo, and what is effects from the creatine, caffeine, etc.
As far as training goes, I disagree somewhat. You don't want to keep training once you've already given your body the strongest stimulus for growth that it will
get ... That's where overtraining comes in, and why most bodybuilders advocate that your lifting sessions be about an hour long. You do need to push yourself beyond your current limits though, either through high volume or lifting to physical failure. And beyond that, you need to figure out your own body's energy needs and what ratio of protein/fat/carbs you grow the best with. For that matter, you have to see how fast your own body recovers, thus how much rest and how much training frequency is appropriate for you.
Or you can be lazy and let a personal trainer observe you and come up with solutions for you.