Let's see.... So here's a breakdown of planning for my current most-active projects:
1. Q.O.C.: It's been in development for nearly 3 years now, and the first year was entirely spent on planning the story from it's beginning to it's middle arcs. This planning ranged from location, cast, and chapters as well. Though the next two years would serve to differ from the plan, the plan still remains a guiding spine for the story as it grows. Though the meat of the story may change, the spine still guides it forward.
2. NORSAN: A newer story which is still being developed, I'm working up a light history and have already formed a cast list, location, and am mulling over a loose map which is literally a blank page with names where locations are. We have a few days before we break into Chapter Planning.
3. IN DREAMS: The One Project which is allowed no plan. Likely once this first arc is finished, and the three perspectives which are being written separately are spliced together, I'll treat the story more formally. In a way this whole project's beginning is all a first go, an experiment with characters, setting, and the plot, seeing if the ideas mesh well. Once it's done, I can tear it apart in evaluation and prepare to write something proper.
Each of my projects goes through several stages:
1. Mulling: Gathering Ideas, The Occasional Experimental Chapter or two.
2. Pre-Visualization: Historical Work, Location Setting, Cast Listing, Chapter-Planning, more Experiments if necessary.
3. Production: Executing on the Plans, writing the first section, reviewing, rewriting, reviewing, noting necessary changes. Eventual Drafting based on the previous notes, drafting for grammatical and paragraphical correctness.
Now planning the story can take quite some time, or quite a little time. Depends on the story itself, sometimes you won't even need time, just a week where your mind is oddly focused. Just jot down your ideas on a page, and if it's strong enough, try a chapter, but call it an Experiment. Always know the first chapter may be lacking, whether it looks perfect or not, give it time, reread it, see what works, what doesn't, see if it's a good beginning, and work with it. Plan from there.
Experiment, even if you know it won't sound too good, you don't know that until you've written it. You need that experiment out first to see what you've got to work with, what needs changing, what works, what doesn't. It's not an easy process, but a necessary one.
I can't say an exact time, though my reasoning for giving QOC an entire year of planning was because at the time it was not the primary project at hand. Furthermore, I really wanted to plan each chapter for a bit, see which direction the story would flow. Note, that you should keep each chapter plan while informative, also a bit vague. And don't constrain yourself to it once you're writing it. See where the characters go naturally, it's an odd thing to say, but think about what makes sense to the character and their personality. A Plan may sound good at first, but once a character starts to actually take off, sometimes the plan will conflict with the personality. A Introvert should not be doing an extroverted thing, but if they do so, they should not be good at it.
QOC is a big example of that. I planned 18 chapters, but in writing I introduced new elements which necessitated a rewrite, and now we've got a much larger, and quite different plan and now 22 chapters written, and we're barely halfway from where the previous 18 were.
Not saying it's bad to plan, plans are good to keep a project going long-term, but once you're writing, don't be shy to pursue beyond the plan if in writing it feels insufficient.
Good Luck, those first projects are the hardest, don't try and tackle it all though, take breaks. Even a single page is something worth congratulating. Listen to some music which fits the mood of the story, it helps. Watch videos, or read something which also puts you in the story's feel of sorts. Not direct inspiration, more so an odd ambience effect. Something which activates and helps the creative flow. You can't control inspiration of course, so try listening, reading, or seeing new things, anything, you never know where the next idea comes from.
