I very seldom compose anything in my head which later finds its way into text, except character names sometimes - I'm often very much inspired by things that I misunderstand.
When I start writing a new imaginary future, I have no idea what it is. The characters arrive first. They help me figure out where they are living and I get to fill in the gaps with that and where we are. So when I get to the end of the process of composition, if I feel that I have really done my job, I have no idea what I've got - and I then spend essentially the rest of my life figuring out what it might mean.
Part of the core of my system, is a way of trying to give the characters more control. If I'm practicing making up what the characters will do, it's never good. In fact, when I catch myself doing that, I try to get rid of that section, and try and let them start making the decisions.
