Part 2--in which I talk about actually starting work on the book. Okay so this is a bit of cheat because I do do some of the initial writing in tandem with the earlier stuff.
Three Chapters: At some point in the process, beginning as early as halfway through basic blocking or anywhere thereafter, I need to actually start writing the book so that I can get a handle on who my characters are and the style I'm going to use to write the story. I find that I am often surprised about some of the details of the story and characters both here and later, despite the fact that I have a very good idea of what the story will look like in overview. I typically start these chapters during the blocking process and finish them in tandem with the basic narrative outline as the two inform each other.
Note: Three is not entirely an arbitrary number, because the basic book proposal format is three chapters (~50 pages) and a detailed narrative plot outline. As a writing tool, three chapters is purely a suggestion as it may well take longer than this to really figure out where the story is going to go and how it will get there. In an adult-length novel ~100,000 words, I will usually nail this down somewhere between 15-20,000. First time authors would be advised to have a completed manuscript before submitting the proposal version in any case.
Working Outline: This is a very different critter from the narrative outline. Here my goal is not to tell the story to a third party reader, but rather to blueprint it for myself. It will include both the events of the story and the structural reasons for those events. So, it might include something like "Draft student into. Establish teachers, also the student TAs." This tells me that at this point in this chapter I need to write several short scenes showing my lead character in his classes. One of the purposes of these scenes is to establish some of my other characters and make them distinct. The depth of description in a working outline will vary widely from author to author and should include everything that you think is important in the scene at the minimum level of detail necessary for you to remember it. This isn't the story itself and all the time I spend here is time that I don't have to work on the actual finished product. Generally, the more inexperienced the writer, the greater the detail they should put into this sort of outline.
A working outline should at the very least lay out all the major events. In my case, I like to lay it out chapter by chapter. For Black School what I did was looked at my first three chapters to get an idea of what my chapter length was going to be (this can vary wildly depending on the story) and then mapped it against the max number of words. YA is short: 30,000 at the low end up to 75,000 at the extreme high end. I chose to shoot for 60,000 as a ceiling and to bring it in shorter if possible. That meant 16-20 chapters. Just getting in all the events listed in the narrative outline took about 14 chapters leaving me 2-6 chapters for unexpected surprises. I determined this by looking at the events in the narrative outline and seeing how much space they had taken up in my three demonstration chapters. This is an extremely inexact science, as one event might be a paragraph in narrative because of its importance, but only a short scene in text, while another might be a sentence in narrative, but a chapter and a half in text.
To Be Continued As always YMMV, and comments questions and anything else you might want to throw in the ring is welcome.