Research film festivals either by location or genre. There are many film festivals all over the country, both large and small, so be sure to choose carefully depending on the experiences you want to have there. Spout.com is a great member driven site about festivals all over the country.
Find out everything you can about the festival you have chosen. It is more than one day? Where is it located? How many people are expected? What films are they showing? What other events are going on during the festival?
Make your travel plans. Based on the information you gathered in step two, you should know where you need a flight, hotel room, rental car and/or tickets to the festival.
Volunteer to work at a film festival. This is a great way to meet people and enjoy the festival without paying for tickets. It also gives you an inside look to what it takes to put at a film festival.