I think it is a very good idea to post your show schedule on your blog, your facebook and to let all of your friends and family know. A great idea is to have a mailing list and to send an email out at the beginning of each month to let people know where you will be and when. You could include a link to the show's website and directions. To get people to sign up for your newsletter, you could leave a book out at shows and ask people to write their name and email address. If you want, you could give incentive. I may give a small print or a glass magnet to each person who signs up. On line I have blog contests and that seems to work well. I am always telling people about my mailing list, otherwise they forget about me. I can remind them that I exist and let them know about promotions, shows and new art.
Make sure that you have enough business cards and packaging to wrap your goodies in for your customers. Make sure everything is cohesive. You don't want to have a pink and green business card and blue packaging. Think of coca cola, everything is black and red. Pick a logo and colors and stick with them.
Something that I sometimes conveniently forget, is the condition of your vehicle. Is your car road ready? If you are traveling far, will your car make it? Is everything going to fit? I have a teeney jetta, and it's a squeeze, but somehow everything fits.
Your tent and tables should be clean and attractive. People will only stop at your tent if it captures their attention, and even then will only stay for about a minute. You MUST get their attention and you MUST have unique and high quality products. Sorry if this offends anyone, but everyone that I have met that buys handmade does so because they want something unique. People will not return to you if your product falls apart right after they buy it. When you create, the question should be, would I buy this? Bright colors really capture attention, below is a great example.
Talking to people is very important, a simple "Hi" will not do. As a matter of fact, I would avoid saying "Hi". I feel that it scares people off. Instead if you notice that someone is looking at one of your paintings, start a conversation about that, or even about the show. Make it a point to be friendly and talk to everyone that looks at your stuff. It is important to smile and be positive. If you are shy - pretend to be someone who is very outgoing.
Make a list of things to bring. On this list should be the obvious, such as your art or crafts, displays and props, but also lunch, water to drink, change for customers, aspirin and chairs.
If you go to many art shows, make sure that you keep creating and try to change things up a bit. This keeps things fresh and appealing.