You may also get addicted to the feeling of having first-hand contact with your audience, rather than send your beautiful art off into a strange faraway gallery. To make at least the process a bit more known to those who have not done this before, here is my illustrated story of getting ready for an art fair. First you have to find the art fairs you might want to attend. This way you eliminate the burden of travel and you can cry in your own soup in your own home if things don't go well. Check out Art Calendar, Show West, Art Deadlines, and other magazines and listing services for artists to find where the art fairs will be in about 6 months.
Lead time is necessary because of the application process, so plan ahead.
In the above resources, check reviews of past festivals or, ideally, talk to someone who did the fair recently and get opinions. Cancellations are expensive for both you and the fair promoter. But having a good selection of works is imperative if you want people to come visit your lil'ol' booth. Matted works, framed works, both of various sizes and color will provide a good variety in order to make up an attractive and balanced display. You will be surprised how many works a 10 foot x 10 foot display will show, and how poorly a half-empty booth looks.