I can tell you all about what I write before I start writing a draft of a book. But the fact is that I'm in the market at the moment. What I've been doing is inadequate to the way my life works right now. Flux is the kindest word I can conjure. Here's what I've done in the past, though:
Nothing. I jump in. I usually have a concept. From that concept, I see if I can write three chapters as a proof of concept. If I can do that, THEN I stop and go back to pre-writing work. That comes in the form of super in-depth character templates. I use the ones from Break into Fiction by Mary Buckham. They begin and end with what drives your characters. It's a lot of psychology and delving into old psychic wounds. It's really great if you're a character driven writer. It worked brilliantly for me for years - years I didn't have an overwhelming full time job, and aging parents living with me. It worked when I had time and brain space for staying immersed in the characters and their feelz.
Those days are gone for the moment. I can either admit that, or I can go on wasting my life waiting for it to 'get better'. What I need now is a means for adding a plot outline or a necessary scene list so I can maximize the tiny windows of writing time I do have. The downfall of the character templates is that they leave your story open - you can still pants your way through a book with character drives and emotions and wounds. That's fine - it's just a bigger investment in time, in my experience. Lovely if you have the privilege. Less so if you're working three jobs.
Maybe this is where writing goes from being self-indulgent fun thing to wallow around in and explore. Maybe under duress, it grows up into something a little more -- I don't know. Packaged? I feel like I'm asking for creative briefs for my own content. Oh hey, did I mention I'm a technical writer for the day job? Yeah. That's all packaged. It's my job to interview the person who hired us and find out what they want in a piece of writing (and when and for how much). Then I find out what source material they have to teach me and the other writers about the product we'll write about. I'm proposing using the character templates as my source material to teach me about my own content. My goal now is to come up with a clearly defined definition of what's required in the end product based on what I know from the source material and what I know about what I'll find fun and interesting about the story.
I mean it *sounds* like a good idea.
Here's hoping it'll do the job. Cause what's happening (or not) right now, just ain't working.