I am adapting my novel manuscript to a film script. I imagine it will take a whole host of other people to tell me how successful I might be. I've done this twice before, and realize that I must not only ignore my usual method of writing, but often go exactly against it.
I attempted to "learn" how to write for film, with many instruction books, and classes, and workshops, and meetings with people. I read many film scripts, which did help me accept the (to my eye) arcane format. But the one thing which turned me visual was the comment of a writer/editor friend who said, after reading my attempt, "I can't see it." That is, it did not cause visual action in her mind. And I understood.
Perhaps the biggest hurdle is to accept that a movie is not a book, and that changes, additions and omissions will be necessary. As with a play, there is a finite time limit which generally clocks in under two hours. The threads and plot points of a movie are different. And the characters (I swear) feel this freedom and choose to accentuate other aspects of themselves than revealed in a novel.
The very fact their paragraphs of dialogue are best reduced to two or three lines makes them uppity. And because they can, in mere seconds, be in diverse locations performing radically different actions, they become exact without apology. They don't have to fill in the spaces.
The writer has to fill in the spaces however, and do so with visual stimulation. The transitions have to be swift and their descriptions exact. The road is always the fast lane and the characters kick the tires with gusto.