It's not enough to be watching something on one screen. You must also, these days, be busily working something on a second screen, probably a small one that fits in your hand.
If you can't sell something they like, make sure they hate it
If you strip away the fancy cars and the overgenerous severance packages, most of what happens here in Hollywood can be put in the category of "sales". The guy at the upscale electronics store trying to sell you the flat-screen television isn't much different from the talent agent trying to package a movie, or the writer trying to sell a pitch.
One of the chief ironies of this most ironic business is that your reward for successfully selling something - you sell a script or a movie, say, to an executive in an office suite - is that you then have to figure out how to sell it to a big and totally uninterested audience at large, who don't drive overpriced automobiles or drink expensive European mineral water.
The model of the film business is a lot simpler to crack, because those guys have managed to figure out a way to get customers' money first. Only then, after you've forked over your cash and paid for an overpriced snack and fumbled your way to your seat in the dark - only then do they roll the first reel of the unfunny comedy or unscary thriller or unromantic romantic comedy.
But by then, you've parked and paid and are two sips into your $16 (Dh60) Diet Coke and you think, "What the heck. May as well stick around. It's gotta get better, right?"
The television business, on the other hand, is ruled by the most violent and unforgiving body part: the human thumb.
Nothing is more terrifying to me - and my bank account - than the human thumb, poised executioner-like over the remote control, ready to zap instantly to something else; something better or funnier or scarier, or just something different.
In the television business, the audience sits on their soft cushions in their living rooms, while the performers are granted a brief window on the screen to please and delight. And the thumb is always at the ready.
So, inevitably, you lose some thumbs in the course of a show. People flip around. Which means you need to start with as many thumbs as possible. There's a lot of complicated and often fraudulent maths involved, but the basic premise is: start with a wide base of appeal.
In olden times - and for our purposes, olden times is defined as when I started in the business - you had no way of knowing, really, what the audience thought about your show. You just had to extrapolate from pointless focus groups and gut instinct.
Now, though, you can simply enter your show's name into Twitter and follow the hashtag to see what people are saying about your work at the very moment it's being broadcast. In other words, you don't need a focus group anymore. Twitter is a continual and merciless focus group, available anytime.
I have a show on the air at the moment, and since it's been a while since the olden times, I hadn't fully experienced Twitter as a promotional and market research tool.
On the night of the premiere, it was gratifying to see positive and happy tweets about my year's work, and I kept refreshing and refreshing to see people liking the characters, retweeting some of the jokes, enjoying the show. I clicked randomly on some of the names and sent them good thoughts, and I did the same with the (relatively) few haters out there.
This is what people in the media business have called the "second screen". It's not enough, I guess, to be watching something on one screen. You must also, these days, be busily working something on a second screen, probably a small one that fits in your hand.
The majority of the tweets about my television show were very positive, and when our sixth episode airs this week, I'm pretty confident we'll deliver up a robust - and almost thumb-proof - audience.
Although I'm not sure it matters.
Because, as I've learnt, if the audience hates your show and is tweeting about it, it means that their thumbs are occupied with the second screen.
And I'd rather have them use their thumbs tweeting about how much they hate my show then using their thumbs to find something else to watch. And that's one thing that today has over the olden times: we've given the terrible thumb something to do.
Rob Long is a writer and producer based in Hollywood. On Twitter: @rbcl