I do not sell in art shows but I have a lot of customers that do. Here are two great resources for art shows:

http://artshowforums.com/forum/
http://www.artfairinsiders.com/

Some artists like selling big stuff, some like small stuff. Small stuff allows you to have a lower cost and can help increase volumes. I saw one person mention they like selling 5x7 and it helps distinguish them from the others that are mostly selling only large items. You have to be careful with going below 8x10 to ensure your margins can support you labor.

Most of the sales are unframed prints, typically matted and displayed in clearbags. Some sales are framed images but mostly the framed images are used to decorate the walls of the booth and help attract customers into your booth. You want to mat the images to a standard frame size so that your customers are not forced to a custom frame shop to get them framed. Most DIY frame supply companies can sell mats with special opening sizes and standard frame sizes.

Trying to rely on the education of customers is not something I recommend for any business. Most people are not looking to be educated by other people. Ever try to teach someone about driving when you are on the road? Of course, there are exceptions and those people will find your knowledge useful and it will help them feel comfortable with their purchase.

Cheers,
Mark