Theatrical Ettiquette

Having spent a lot of time in various theaters (on both sides of the footlights), I have come to realize that the average theater audience these days is, uh, below average. The common theater-goer nowadays, influenced by television and movies, has small idea how to behave at a theatrical performance. They must come armed with refreshments (alcoholic and non-alcoholic) which they bought at the refreshment stand in the lobby. (NOTE: most theaters depend on that refreshment stand to make up the difference in the plummeting ticket sales.) They come dressed in well-nigh anything; the days of dressing up to go to the theater are long gone! They begrudge the request to shut off their phones, as they have plans to record the whole show on said phone. And They somehow don't like the seats they are supposed to sit in. No sooner are they seated than they are trying to wheedle a better seat that happens to be empty. Or they stand next to the seat, as if guarding it, and block the aisles by gathering friends, chance acquaintances and total strangers in a group to talk about- nothing!
So here are some elementary etiquette tips for attending a theatrical performance.
(1) ARRIVE ON TIME. Yes, there are provisions for seating a late-comer, but (especially if your seat is in the middle of the row- as it usually is) you are inconveniencing the other members of the audience, and bothering the actors who are trying to get the show started. Yeah, they know what you're up to, even if they can't see you clearly in the dark. And as an addendum, don't hang out in the lobby until curtain time. You're holding back while you have one more drink, and, well, see the above comments on seating late-comers.
(2) IF YOU NEED TO LEAVE DURING THE PERFORMANCE, DO IT AS QUIETLY AND DISCRETELY AS POSSIBLE. That means going out the back exit, not walking down front by the stage where everyone sees you and ignores what's going on in the play in the meantime.
(3) WHEN THE PERFORMANCE IS OVER, SHOW YOUR APPRECIATION IN THE APPROPRIATE MANNER. Clap, whistle, or none of the above. A standing ovation is not automatically expected, unless it is deserved. Either people today are more easily amused by live performances, or they have developed a completely wrong idea as  to what a standing ovation means.
(4) BY ALL MEANS, GO TO AS MUCH LIVE THEATER AS YOU CAN. My remarks should not be a discouragement or inducement to limit yourself to what you can find on television or DVD. there is something about a live performance that cannot be captured by a recording, no matter how good the performer.