How to do a Book Signing:

1. Have no expectations about number of people who will be there.
2. It's nice if the bookstore has a poster up about the event and a table ready for you. But be warned: they won't always.
3. There should be books for you to sign. You shouldn't have to bring your own. (Nonetheless, sometimes I've had to do this because a bookstore was just plain stupid.)
4. Speak nicely to the bookstore people (or library people). These are the people who will be selling your book for you after you're gone. This is probably the most important part of a book signing.
5. If people come to your book signing, make sure they feel they have gotten your attention. Don't act bored.
6. If possible, sign with other authors so you have someone to talk to. But don't talk while people are waiting for a book to be signed.
7. If people treat you like you are staff at the bookstore (it happens all the time), just gently direct them to the actual staff to deal with their questions.
8. Offer to sign stock before you leave, but don't be offended if they don't take you up on the offer.
9. Send a nice thank you note or email to whoever invited you afterward. Even if you didn't sell a single book, it was nice for them to invite you.
10. Start planning what you can do better at the next signing. It's partly your responsibility to get people there.