You’re listening to the radio; talking to your friend; overhear a conversation in a café; read an intriguing fact. All of a sudden an idea comes. You wonder what if. The idea strikes.
How do you go about turning that idea into a story? The first step is to expand the idea.
You hear Li’l Red Riding Hood (Sam the Sham and the Pharoahs (1966) Lyrics written by Ronald Blackwell.) on the oldies station and all of a sudden you decide to have a female protagonist. What kind of story do you enjoy reading? What types of films are in your library? In other words, what is your favorite genre? Action? Mystery? Psychological thriller? Is Red going to be edgy and street smart, voluptuous and ready and willing, sleek and sultry? Is she naïve but smart? Lovable but needs protection?
Is the wolfish villain going to match her or be her opposite? Sophisticated and charming? A menacing gangster? A diamond in the rough Harley rider? Maybe he rides an old Indian. Naw, not a villain. Does he keep his sheep suit on until the end, or does she know right away?
Where does the story take place? Is she in L.A. on her way to Ohio? Is it an historical piece? Maybe she really does live on a small farm near the woods. Does she hang out at jazz clubs in New Orleans and Grandma lives across the lake?
And what about the Woodsman? How does she meet him? What does he look like? Is he a double-barreled hunk? Retiring and stoic but rises to the call? And what about Granny? Do you see how this process goes? Questions, questions, questions. Does Red actually get rescued by the Woodsman? Or, like some French versions of the folk tale, does she get rid of the wolf by means of her own smarts?
At this stage you just keep asking questions and coming up with answers. When you are clear on all the various attributes, write it all out. Your idea is now expanded into the basic elements of your story. No process is carved in stone; each writer develops their own way of putting things together. But especially for a beginning writer, having a traditional process as a guideline at least gets you going.