Always keep your feet on the floor and not on the balcony or seat in front of you. If you need to unwrap medications and cough suppressants, do so during loud musical numbers, applause and laughing. There are a number of rules when applauding. You can shout Brava or Bravo to excellent performers. The conductor is also applauded when he enters at the beginning. You can applaud very well or give a standing ovation to very good performances.
When the performance ends, do not immediately aim for the exit. Wait for the actors to exit the stage entirely before leaving. Make sure you follow the minimum age limit if you intend to bring kids. Always orient your children about what to expect and teach them about proper manners and how to behave inside the theatre. Feed them and have them go to the bathroom before the start of the performance. Give them some light snacks and bring them back to the bathroom during intermission. Most theatres recommend that you do not bring children younger than 4 years old to the theatre. Never videotape the performance.