Prepare yourself by conducting a little research prior to attending an opera. Reading a short synopsis will provide information on the plot, main characters and setting of the performance you are about to experience. If making a first visit to the opera house, it may also be beneficial to preview opera music and familiarize yourself with opera terminology in advance.
Dress comfortably. One popular misconception surrounding the opera is that it is to be enjoyed by formally dressed elite upper-class citizens only. This could not be further from the truth, and opera houses encourage patrons to dress for comfort. At any given performance, guests will dress in anything from blue jeans to evening gowns, though most attendees settle somewhere in between with business attire.
Behave suitably. Opera performances begin promptly as scheduled. In most venues, latecomers are not permitted to enter the auditorium until a scheduled intermission. Also, any person who leaves the auditorium during the performance will not be allowed to re-enter until an appropriate interval. Out of respect for fellow opera patrons, it is also advised that visitors do not whisper, talk, eat, take photographs, make recordings, communicate with cell phones or use any other electronic devices during the performance.
Applaud when the performance moves you. Of course, if you are shy or concerned about being inappropriate with your clapping, follow the rest of the audience when offering applause. A general rule of thumb is to clap when the conductor emerges to begin an overture, at the end of an act, at the end of the opera and when the performers take their bows. Further appreciation for the performers can be shown by shouting "Brava!" for female vocalists, "Bravo!" for males, "Bravi!" for an ensemble or "Brave" for an all-female group of performers.