First and foremost, I would say that whatever I do wouldn't apply to everyone so I would to remind you to keep that in mind.At first, I decide the core facts like "what is the story about?".A key/core message makes things easier to work upon. The key message can be as simple as possible e. g. something you can summarize in one line.Taking Heavensward as an example, this is the story about the war between the dragons and the humans which lasted for a millennia.And then I elaborate on that and create questions like "What is this war that lasted 1000 years?" or "Why this war had to happen?" or "What's the difference between dragons and humans?" and then I will create answers for that.Then I decide an order at which point these questions are answered. During the process I can see the roles for the characters that needs to play.For instance, taking Estinien as an example he was needed as kind of a mean to explain what kind of country Ishgard is and also the point of view from Ishgardian side and then we elaborate on those.How much I write depends on how much I can concentrate on writing. If I don't need to work on many other things, I would concentrate on one thing.Back in the time when I was working on Heavensward, I was working on everything but I can remember that I created tank quests in one day.As for the main plot which is two years planned beforehand, Yoshida would be the best person to talk about it.