This article by Larry James includes some great ideas, including:
DON'T - Don't just sit at the table they have for you. Most authors do that. Be different! I always tell the person booking the signing not to worry about putting a chair behind the table. This will always get their attention. Let them know you will be the store's official greeter while you are there. Walk around the store with several copies of your book and introduce yourself to everyone. If those you introduce yourself to show the least bit of interest, hand them a book. They will almost always take it. Tell them to look at it and bring it back to the table when they are finished. On average, I more than tripled my book sales at signings by implementing this tip!
DO - Have your book covers enlarged in color to an 11 x 17 poster, laminate them and have them put them on a poster type board with a stand up thing on the back. Always bring them with you to the signings! Anything else you can think of to call attention to your table is also GREAT!
DON'T - Don't complain if you don't sell lots of books. Signings make those who bought your book feel good, but they really don't sell lots of books while you are there, UNLESS you create a presence WHILE YOU ARE THERE! I've sold as few as none to as many as 56 in a two hour period. According to book store managers, on average, book sales for a non-celebrity author will range from about 4 to 7. If you sell more, you're doing great!and
DO - Get there no less than 15 to 20 minutes early and if you can, stay late. At a signing in Tucson, I sold more books in the extra 30 minutes after the signing than in the previous two hours.
Check out the full article here.
Illustrate and Write On,