When I'm working on the first draft of a story, at some point the narrator of the tale steps forward, and begins dictating the text to me. Not in any coherent order, though. So it is imperative that I write down immediately every word at the time I hear it; because the dictation seems to float out of my head as quickly as it floats in. And the dictation won't happen when I am sitting at my desk, with a pencil in hand. Not at all. My narrator is the most verbal when I am walking---physically moving. Or when I am between sleeping and waking.
Three things help me catch hold of these skittish dictations. In my living room, directly in the path of traffic, is my antique schoolmaster's desk. It's a matter of only a few seconds for me to pause at the desk, jot down the phrases I've just heard, then continue on my way.
If I want to really encourage my narrator to talk to me, I can take a walk or a hike. For this I hang a notebook on a ribbon around my neck. The pencil fits perfectly into the spiral binding. And I am, once again, prepared to jot down instantly anything that my narrator might have to say, hardly breaking my stride as I do so.
And in the middle of the night, when my narrator is feeling especially loquacious, and I am barely conscious? I found that if I sat up, turned on the light, looked for my glasses, and groped for a blank page in my notebook, my narrator would have already quit in disgust. Instead I keep this three-ring notebook under my pillow, with the pencil clipped to a blank page. When my narrator begins, I do not turn on the light, or even open my eyes. Instead I stealthily pull the notebook from under my pillow---all the while listening intently to my narrator---open to the marked page, and transcribe in the dark. I've learned to put just a few lines on each page, then turn to the next page and continue, so as to end up with something that will be relatively legible the next morning.
I find this method really annoying at times---so inefficient! And especially when my narrator keeps waking me up at night because there's "just one more thing" to tell me. But it does get a story started. And I've never discovered a better way for myself.