My kids looked at me and asked how I knew that. And I said I just knew. "Actually, no, it's more than that," I said. "It's because that's how I would've written it."
I never used to be able to do that. Or only very occasionally. But the longer I've been writing, the more I have my prediction-meter turned on. At some point in the TV show, or movie or whatever, I'll just know.
Of course, I'm not always right, and the best films and shows are the ones that don't end up where I've predicted, that subvert my expectations and surprise me. I'm not talking the old-fashioned twist ending here, but an ending that grows out of the characters and the story.
The best writers don't settle for the predictable. They toss away the first idea that comes into their heads and explore other options. The best way to do this is with the "what if?" question. What if this happens? Plot out the likely chain of events. What if that happened? What about something else? Each time you ask that question, you'll move into more original territory. We shouldn't settle for the first idea, but nor should we for the second or third either.
The further we push, the deeper we explore, the fresher and better our writing will be. If we're scriptwriters, we won't have audience members like me who've worked out the plot halfway through the movie. If we're novelists, we may still have people who flick to the end of the book (there's no getting away from them), but they'll see it doesn't end where they thought and so will still need to read on to see how we got there. But the best part of all is that we'll have something we know is ours and is good, something we can be proud of.