When I set up my Mac Pro I created an alternate, internal drive that could also be used as a startup drive. I realize that I forget some of the keyboard commands for diagnostic startups, and recognize the inability to research them in crisis when a computer fails to work correctly. I am wondering how some of you may have prepared for such a possibility. Do you create any sort of references on paper? I also consider this as I ponder whether to create an alternate drive so I can try Mountain Lion and at the same time keep a drive with Snow Leopard in case I want to go back. Thoughts?