Festival rules are called by a couple BEFORE arriving at any large public gathering (concert, music festival, sporting event, etc.) Both must agree that Festival rules apply. Once agreed, the first person to see someone they know must call them by name and get a mutual acknowledgement that you do, in fact, know each other. You MUST know the person's name, and they must know yours. If you are the first to win, you get to name your prize, usually your favorite sexual position or favor.
A couple agrees to Festival Rules on the way to state fair. At the fair he sees an old friend and calls her name. The friend acknowledges him. He wins sexual favor for the evening.