(Image source here.)
In 1953, John Cassavetes knew practically nothing about writing. Sam Shaw decided to help him by introducing him to Edward McSorley, a novelist, who gave him a crash-course in screenwriting. Cassavetes said that McSorley taught him the three most important things he knew:
1. That character was more important than plot, and that the most important thing of all was to present characters truthfully.
2. That the artist should not explain or define too much, or "do too much thinking for the audience," but that the story should "evolve, so that people could understand it only gradually as it went along."
3. That "style is truth" and all that really mattered was that every scene should be as true to life, truthful about the characters and their real feelings and behavior, as possible.
Big thanks to A John Cassavetes Fan Site!