What is a reasonable number of books to bring to a signing, in your opinion? I know some authors have a 3-book thing, or a 3-books and then the back of the line thing... Just curious.

I have never had a limit, and doubt that I ever shall. The only thing like that I ever did was (back when I wrote comics) ask people to please have bagged comics out of the bags, as it slows me down, having to open them, and I don't want to run the risk of doing to books damage, opening the bags.