Season brochures often have a reply form, on which you can mark the concerts you want to attend and the seat price you desire. Sometimes you can fax your order. Usually you can't pick your seat with this method, but you can specify a section of the theater. If you buy your ticket in person, the salesperson will hand it to you. If you buy your ticket by phone or mail, the ticket will be mailed to you or held at the box office, where you can pick it up on concert night.
Tickets are usually non-refundable.
Most tickets are non-refundable, so you probably won't get your money back. If you are a subscriber, you might be able to exchange your ticket for another time. Call the box office to check their policy. Ticket prices vary from zero to more than a hundred dollars. Large theaters have more than one ticket price.