Read the ticket stub from your theater purchase. You'll need it for the remaining steps. If the ticket stub does not have seating information on it, contact the theater for assistance in locating the seat.
Visit the theater's website. Usually the theater's website contains a seating chart of the auditorium. You can use it to determine where you will be sitting in the theater.
Arrange to sit in the theater seats you've been assigned when there isn't a show. You can usually go to the theater and ask if this is possible. Determine how much of the stage you can see. Alternatively, you can catch another show and try to sit in the seats for a few minutes to determine how good they are. Make sure you can hear well and see the action on the stage adequately.