Copyright 2011 by Gary L. Pullman
A common question that aspiring writers ask the pros is "Where do you get your ideas?" Stephen King claims he gets his in a little shop in Utica, but the true answer to the question is that he gets his ideas from the same sources as every other writer, aspiring or pro: from dreams, mental images, newspaper headlines, reading, anecdotes told by others, personal observations, song lyrics, classroom lectures, history--the list is all but limitless.
But what one more than likely means, perhaps, to ask by this question is "How do you develop your ideas into stories?" The answer is simple, really: bring together person, place, and thing.
The person is the story's main character, or protagonist.
The story's place is its setting.
The story's thing is its theme.
What brings the three of them together is the story's conflict and the main character's attempts to resolve this conflict, which includes both his reason, or motive for doing.
Another way of= saying the same thing is to say that a writer develops a story idea into a story by answering six questions: who? (protagonist), what? (conflict), when? and where? (setting), how? (resolution), and why? (motivation and theme). Here's an example:
Idea: A girl is possessed by the devil.
Who? Father Damien Karras, a priest who doubts his faith (protagonist)
What? fights the devil (conflict)
When? and where? in a Georgetown townhouse (setting)
How? using exorcism (resolution)
Why? to save a possessed girl's soul and retain his own teetering faith in God (motivation and theme).
That's how it's done and why.
(There's a fill-in-the-blank way of developing the scenes of a story, too, which I explain in "The Fill-in-the-Blank Guide to Writing Fiction").