The other day, Nathan Bransford posed the question: "How much can you talk about your idea before you write it?" Some writers are energized by talking about the story; it helps them generate enthusiasm and new ideas. But for me, the answer has always been: Not much. About works in first draft, the most specific I tend to be is, "It's a young-adult novel" or, "I'm working on a short story."
Writing a first draft takes a lot of energy. Creating a world from scratch requires an incredible amount of concentration and tension. I discovered early on in my writing life that if I talked a lot about a story I hadn't finished yet, I tended to lose interest in ever finishing it. I left the fight in the locker room, so to speak. Also, it can take me a while to figure out exactly what it is that I'm writing--the characters surprise me all the time. I may discover in chapter 16 that my main character is adopted and has been wondering about his biological identity all along, and that's what the story is really about.*
The farther along I am, the more I can say about a story. Once it reaches the third or fourth draft, I can squeeze out a one-word description: a topic, perhaps, or even a one-line summary. A few drafts later, it's ready for critique and I not only tolerate, but require, lengthy analyses and discussions of how the book is constructed and what it's about. When it's finished, it's a pleasure to discuss the story with readers--at that point, I could talk about the book all day. But early on, that seed needs silence to germinate.
*Naturally, this is not at all what my current work in progress is about. I don't think.