As a working screenwriter and a screenwriting teacher, I've developed some strong opinions about what students initially don't understand and need to know about screenwriting. I've developed these ideas most completely in my electronic screenwriting tutorial Screenwright: the craft of screenwriting, which in turn was developed from the screenwriting website I had online from 1994-2001. Here are some highlights.
I think there's an order to what screenwriting students should learn; first things first. In my University classes, I follow this order:
Reality 101. Most students begin their studies with wrong and romantic notions of what screenwriting is like. First, then, I treat my students to some war stories about what the screenwriting life is really about. Screenwriting is unlike any other kind of writing, sometimes in ways not flattering to the writer, and it's important that the students know this from the beginning.
Story Concept. Hollywood is concept-driven, a spinoff of Reality 101, and the student must understand what this means in terms of creating a screenplay that has a shot at making it to the screen. I don't insist that students write "high concept" commercial material but I do insist that they understand how the screenplay market works -- and how it is changing, potentially a great deal as a result of digital technology.
Screenplay Rhetoric. This is the area where beginners have the most trouble. Almost all students over-write because they don't understand how compressed and "minimalist" spec screenplay rhetoric is. Good models are surprisingly difficult to find because published screenplays are shooting scripts, not spec scripts (the term for the scripts written "on speculation" by writers), and because the evolution of screenplay rhetoric is not always reflected in the writing of established professionals.
Story Structure. In western culture, stories are told with a definite dramatic structure, often called three-act structure, and nowhere is this as visible as in screenwriting. Why? Because in the screenplay the dramatic structure has a thinner shield of rhetoric to hide it. Many of my students are novelists who study screenwriting in order to beef up their skills in dramatic storytelling.
Scene Efficiency. Story structure is about the big picture. Scene efficiency is about the small picture. Next to rhetoric, this is the area where beginners have the most to learn. They typically begin scenes far too early and end scenes too late. Most scenes in a movie are under a minute long! Don't believe me? Take a stopwatch to your next movie. Hollywood has mastered the craft of scene efficiency, and even poor movies usually provide good examples of how efficiently film stories get told.
Writing As Process. Most students commit themselves to their first story ideas. They are too defensive of their first takes on the material. All writing is a process but screenwriters especially must learn to be flexible and ready to change material in major ways (see "collaboration" below). They first should learn to do this on their own, in the rewriting process. Allow yourself to be bad because everything, everything!, can be changed later. No one writes a good first draft of a screenplay. Writing is rewriting.
Writing as Collaboration. There's a good and bad sense of collaboration in terms of screenwriting. In the former, screenwriting lends itself to writing with a partner or partners more than any other kind of writing, perhaps because screenwriting is less dependent on rhetoric and more dependent on story telling (i.e. dramatic structure) than other kinds of writing. Screenwriting especially lends itself to brain-storming in the early, story-creation stages. In the poor sense, eventually the screenwriter will be rewriting in collaboration with a producer and/or director and in this marriage the writer is the least powerful link. In fact, screenwriters are often fired from their own scripts because they won't make changes requested by a producer or director. This is another aspect of Reality 101 and an important one. The artistic standing of the screenwriter is low and the opposite of the playwright's standing. For example, playwrights never sell their plays -- they lease them. No one legally can change a word in a play script without the playwright's permission because the playwright always owns the material. The screenwriter, however, sells the screenplay -- whoever buys it, usually a producer, can change it in any way. Screenwriters, in this sense, are powerless.
Marketing Skills. Most screenwriters prefer writing to marketing but without marketing skills, a student gets nowhere with a finished script. There are definite marketing skills to learn and strategies to consider.
Endurance. When I look at my students who are successful in screenwriting, I find that the determining factor is not talent but endurance: the writers who "make it" are the ones who don't give up, and these aren't always the most talented screenwriters in my classes. There may be no more difficult and competitive area of writing than screenwriting. Success doesn't come easy (Reality 101 again!), but every year there are new screenwriters who get their scripts to screen, so it can be done. You can help your chances at success considerably if you move to L.A. (Reality 101), but spec scripts can be sold from afar as well, it's just more difficult. The key is not giving up. Keep studying both the craft and the marketplace (Reality 101), and keep writing.
Here are some other links to help you in your pursuit of a screenwriting career: