If you're one of those crazy book authors, Writers Weekly has some advice on making the most out of a reading/signing:

Bring giveaways to your signing. These needn't be expensive, but MUST pertain to the book or its theme. People love events where they get something for nothing. A bookmark, pin, or other small item is a reminder of the event. Even if all attendees don't purchase books, this item may cause them to spread the word about your book at a later date.

People like magnets, for instance.

I have something else to add, meanwhile. I was speaking with an author friend last week about readings, and he advises, always read before you sign. Why? Nobody is there to hear you read. They want to meet you and get you to sign the book and possibly try to get you to read their manuscript. So get the reading part over with first because if you don't, nobody will be there to hear you.