Ideas are written down, somewhere, somehow. The first idea I wrote down was pretty imaginative and ideasy, but I wouldn’t say the idea was ‘mature’. It had to grow somehow or be used in the appropriate way, be that I could make it in something good with the appropriate traditional publisher or if a script the right producer, or go the self-publishing route and all that entails for the author, or hit the delete button, if all else fails. But sometimes ideas just sit there and flounder and do nothing. This is good because they are left to grow as the writer grows as a writer and an author.
As the growing happens and life goes on, the writer may go back to old ideas and compare to the new ideas. Maybe they sound better, but still not ‘mature’.
The writer must keep on growing, all the same. The would-be author can also see what’s out there in terms of ideas and stories, get a “feel” for it. This will help the writer decide if his idea holds up in the marketplace. The ideas in the marketplace are mature. Then the writer can get a sense if his idea is potential for a mature story in the marketplace or not quite there yet.
When a mature idea comes along, or the proper maturing of an idea, I think the writer should know it, as if the “stars aligned”, as one’s whole idea jells with what’s in the marketplace, or the writer at least senses this is the best fitting idea. It’s a natural fit and he knows it, beyond a doubt, even if no one else does.
The next part is writing the story, consciously and deliberately, artistically, to finish the story, and find a publisher.