I didn't plan to do such a long series of posts on book signings, but your questions have been so interesting that I thought I'd press on with yet another one. This is in response to a question about the size of the venue.
Space at small Indies isn't a problem at all. Here is the venue for Montclaire's A Great Good Place for Books. You can see it's "cozy," but the turn out was great for two reasons: people from different ages came and during the Q & A there were a lot of questions.
At larger venues like Books Inc. in San Francisco space was definitely not an issue and the turn out was about 40 people: teens, bloggers, and adults. Jen Laughran did a lot of publicity and offered refreshments. The theme, Debutantes, included tiaras for fun.
Here's another event with five of us (L to R. Sarah Quigley, me, Malinda Lo, Cheryl Herbsman, Jon Yang) at Corte Madera's Kidlitsalon hosted us. This audience was mostly people who wanted to publish either their illustrations or their novels. Some bloggers came as well.
So you can see that the venues are as varied as we are with our books, and the size of the venue isn't something to be concerned about. Getting the word out is.