All you do is sit staring at a blank sheet of paper until the drops of blood form on your forehead.
Most playwrights go wrong on the fifth word.
When you start a play and you type 'Act one, scene one,' your writing is every bit as good as Arthur Miller or Eugene O'Neill or anyone. It's that fifth word where amateurs start to go wrong. Writing a book is a long, exhausting struggle, like a long bout of some painfull illness. One would never undertake such a thing if one were not driven by some demon one can neither resist nor understand. You sell a screenplay like you sell a car.