Granted, when you first come up with a new story idea it's important to pin down the basics of what might motor the script in terms of central character, his or her external want and internal need, the other potential major characters and how they might put up barriers and create the tension and conflict in your central figure's arc or journey, and finally, giving some thought as to where the story might land and what kind of statement that ending is leaving with your audience. This is the way you initially test a new idea to see if it might have the "stuff" needed for you to begin to dig deeper.
However, it's at this point that many writers make a mistake. If they're still excited by the idea, they're eager to push ahead and immediately attempt to invent and develop their plot in some detail, following one or more of the many structural paradigms commonly used in our field. The problem is that they're skipping a critical step in the process, namely stepping back at this point and taking the time to thoroughly explore the backstories of the characters, their voices, and the baggage they bring with them into the story that's going to be the script itself. In other words, getting to know the major players as real people with real pasts who bring to the story unique personalities with powerful emotional memories.
Because it's doing this exploratory work that arms the writer with a rich understanding of that nine-tenths of their story that's going to always be hovering there under the surface. And there's no better way to enter into the plot invention phase of the process than with this exploratory work at your disposal.
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