I've spoken about zero drafts but I haven't really explained what they are.
A first draft is how you were taught to write in school. You have a thesis, which you are seeking to prove. So you start writing in defense of that thesis.
In a zero draft, all you know is that you want to write something, but you don't know exactly what.
The essential philosophy of zero-drafting is that you can't do it wrong. You don't know what you're trying to say. So say anything. When you are done, you will have accomplished your initial goal: you will have written something.
You don't have to apologize for what comes out. You can say, "I don't know what to say," five or fifty or five-hundred times. Say, "I don't know what to say," five-hundred times, and you'll have said something. Believe me.
In a zero-draft, because you don't have to apologize, you can say things poorly. You can leave in misspellings, if you want. You can go back and change things if you want, but you don't have to. You can just write.
As you cannot do it wrong, the zero draft is done when you say it's done.
My winter version of the technique was to just type, to write whatever asked to be written in the moment. I didn't even stop to correct typos (and my text editor doesn't auto-correct). Recently, as I noted in my first post, I have been aiming more directly for publication, and that's changed my zero-drafting a little. But most of the time I still don't bother to correct typos.
"Done" is an interesting question in a zero draft. If you don't know what you're going to say, how do you know that you've said it? I find for me the answer is often that I know I'm done once I've discovered what it was that needed saying in the first place.
But sometimes I know I haven't said it. And I haven't said it not because I haven't tried--I've been zero-drafting, after all, and so I've been saying something--but because I haven't yet figured out how to say it. But rather than letting my not-knowing frighten me into saying nothing, I am saying something.
And maybe that something, too, is worth saying.
In a sense, every zero draft is about not knowing exactly what it's about, and how okay that is.
To dare to believe that something valuable might come out of it is therefore a practice of deep trust and deep vulnerability.