You learn to do your best writing on story rather than off story. Very often at the beginning of their careers, writers including me do their best dialogue writing off story - the best lines, the best observations - but they haven't got enough to do with the plot to stay in.
Victor LevinThe good thing about being in advertising was a lot of the skills cross over: you have to be accountable for your jokes; you have to tell a story quickly. It's the most expensive filmmaking foot-for-foot in the world, so it does teach you how to use all of the machines and how to think of things in terms of the physical process of capturing the images. And you have to sell your work. You have to walk into whatever it is and stand up in the middle of a conference room with a storyboard in your hand and make people laugh.
Victor Levin