How do you know when to play the specific wedding music?

We always begin with fifteen minutes of prelude music at which time we are watching for our cues which are planned ahead of time with the client. Because we are familiar with all of the music and with the musicians with whom we play, it is easy to make eye-contact and come to a graceful end so that the next piece can begin. We know ahead of time who is in the bridal party and the order in which they walk. We also make contact with the officiant so that any special music as part of the ceremony is played at the correct time.