I have a new foster baby. It is a large macbook of my friend's. It's a few years old and kind of busted up, and as he has another, newer one of the same model, he's letting me borrow this one for the rest of the summer. What are common problems and important shortcuts (besides stuff like apple+q; I'm not that unfamiliar) for Macs, especially slightly older ones? What do I need to know to take good care of this thing?