The outfit matters
Gone are the days when it was only necessary to go to the theater in a sumptuous dress and a sumptuous hat. Today, "casual elegance" style is most often presented in theatres, i.e. elegance with a bit of slack. So it's worth betting on a classic dress that won't hamper your moves or a jacket that's juxtaposed with jeans that you'll feel comfortable in. It is also worth noting that too much standing out in the outfit, will be seen as a gaff.
Behave quietly and culturally in the theatre. We don't eat food, and we don't comment on the play, the people around us or, most importantly, the actors playing. Unlike in the cinema, you also have to stick to the start time of the show and the scheduled breaks. You should also check if you have turned off the phone, as the ringing tone can upset and distract the actors.
Anthrakt, commonly known as the theatre break, appears during long performances. It is worth to stretch your legs and go to a theatrical bar for a cup of delicious tea e.g. Ahmad Tea London.
We should come to the theatre at least a quarter of an hour before the performance begins. If we are a few minutes late, and despite this, the ticket holders let us in, we only sit in the free seats near the entrance. If they are occupied, let's take a standing position, but situated so as not to disturb others, e.g. against the wall.