Telling a story or two from your books would be a way to give visitors a "sample" of what else is in your books, but don't give it all away!
You should also discuss why you wrote the book. For example, what motivated you to tell these stories?
Regarding how many books to bring, it will be a bit of trial and error, but it will depend on who's organizing the book signing. Is it you or the book signing venue? If it's the venue, have a chat with them about what they anticipate and then estimate from there. If it's you, don't expect that everyone will buy a copy. If you do run out of books, have some way for them to place an order for a copy.
I wrote a couple of articles on book signing events. Search for these on my profile: "Book Signing Event Tips for Authors" and "Book Signing Event Challenges: Protecting Your Sales and Profits."