My writing process starts with things I think about and talk about with other people. I often mentally hash something out while walking well before I sit down to write.

I also try to collect snippets of things I want to develop at some point and create stubs that I come back to later, sometimes months later. It's something of a collage and sometimes it results in something good. (Made the front page of HN a few times this year, so I think it's better than it used to be. In theory.)