In my private class last night, I was asked, "How do I choose my story?" The answer to that question is another question: When do you choose your story? Do you start writing it first or do you first research what sells?

The most important principle in my method of writing a screenplay is: Create for yourself first. You are your own first audience, and it seems obvious that if you don't like your story, no one else will either. But, sadly, I see so many writers – in their attempts to be commercially successful – take on a story that they think will sell. This can be a savvy choice, but if you are not connected emotionally to your material, it will be many times harder to make the script any good. Also, part of what helps us write screenplays is the knowledge we’ve gained from the hundreds of movies we've seen. So if you decide to write in a genre you don't know or like, please understand that you will end up having to do much more preparation than if you work in a style you know and love.

When you are writing your first draft, let the story tell you what it wants to be. Truly original material can't be judged in advance because it doesn't exist yet, and there are no benchmarks. Write the script however you feel it and then assess it for the marketplace later.

When you are trying to sell your script, you have to tailor your viewpoint and ask yourself if you would pay to see the movie of your screenplay. If you answer that question affirmatively, you must then consider objectively who – and how large – your audience would be. You can research this by comparing your script to completed films and finding out how well they did at the box office. I am not suggesting that you make changes based on this research, but you will get a clear idea of your screenplay's chances.

You can also determine the right people to send your script to by looking at a similar movie’s credits and finding out which producers are already making films like yours. The Internet is your friend – there are many great sites, such as www.imdb.com, with information that will help you sell your screenplay. It’s also important to read trade magazines, but take the information with a grain of salt. Just because a script is being produced that’s similar to yours doesn’t mean you should scrap your idea. You just need to find an original tweak for your plot.

To summarize, in your first draft, let the story and your own interests tell you where to start. Then before putting your script into the marketplace, evaluate your screenplay based on the factors we've just discussed.

If you genuinely like it, others probably will too. But the most important thing to remember is: Don't get it right get it written.