Faculty - Visit them during their office hours, and watch for posters outside of their doors and on bulletin boards. Many are on mailing lists for national organizations and festivals that will also be helpful to you. Networking - Ask friends, teaching assistants, random graduate students about how they've located festival opportunities. Once you've identified the places that interest you, create a calendar to help you meet deadlines, schedule audition dates, etcetera. Whenever possible, audition live rather than via tape.
Many festivals hold auditions in Dallas and Houston.
Allow yourself plenty of time to prepare your application. Don't wait until the last minute to put it together. Factor in the cost of flying to your audition into your budget. This can be an expensive endeavor as most auditions take place on the East Coast. These sites will provide contact information for their respective festivals.