How much of the plot of his novels does Stephen King know before he starts writing? This is what he told Goodreads:
"I start a book like Doctor Sleep [his most recent book] knowing just two things: the basic situation and that the story will create its own patterns naturally and organically if I follow it fairly...and by fairly I mean never forcing characters to do things they wouldn't do in real life...For me, the first draft is all about story. I trust that some other part of me—an undermind—will create certain patterns."
He adds, "The basic pattern of a story or novel should be there in the first draft. Story creates theme; theme suggests certain events; the events become part of the story. Around and around it goes."
What about rewriting?
"When I read it over (after letting it rest and rise, like a good yeast bread dough), I usually see the patterns and can mend the places where they go off on the wrong track or disappear completely."
As proved by the many examples in my book, Your Creative Writing Masterclass, this is only one way of approaching crafting a story. Other authors won't start writing until they've worked out an outline in detail.
To find out what works for you, sometimes first you have to find out what doesn't. Eventually you'll discover the most effective and efficient way for you to write.
I think the crucial thing in the quote above is "never forcing characters to do things they wouldn't do in real life." Of course we're talking about their real life, which doesn't exist but has to seem that it does in your mind before it can exist in the minds of your readers.