If you're looking for a somewhat low-key but pretty good restaurant in North Beach, try Michaelangelo's. The menu is not that extensive, but the ravioli is to die for. I like to get it with a tomato cream sauce (or something like that). After you're meal, they'll provide you with a huge bowl of gummy bears and cookie to wrap up with. It you really think about it, it could be gross with all the potential germs. But just don't do it and enjoy.
It's been a couple of years since I've been in the city, and visited, so the might not be totally correct. The place does get pretty busy, so you may need to wait a bit.