Admission is free, though tickets are required; audience members will be seated both in the stands and on the field. More than 30,000 tickets have already been registered at www.sfopera.com/giants. Anyone interested may still sign up this morning. Ticket holders will be admitted (general seating) at 6:30 p.m.; those who haven't registered ahead of time may enter beginning at 7:00. The pre-game pre-performance programming starts at 7:30, with the curtain going up at around 8:00.