What is the procedure for writing a story?

Start, “Once upon a time,” or “It was a dark and stormy night,” and then go on putting words in a row until you have a complete story.

Seriously, there is no “procedure.” Sit down, open a new Word file or whatever, and write the story. It is sometimes, but not always, helpful to have an idea about what you want to write before you start. There is no procedure for getting ideas either.