I spend an inordinate amount of time thinking about my current WIP; far more time than actually writing it. I think about it as I making dinner, as I'm getting ready for bed, certainly before I go to sleep. I mutter dialogue in the car, which would explain why I am the recipient of the occasional odd look. (actually, that had better be the reason!) I'm happiest when I know where I am in the story so when I actually open up the laptop and start typing I've got a fairly good idea what I'm going to write.
Some writers prefer to create freely. They sit down and let the words flow and let the story lead them instead of them leading the story. Honestly, this method would never ever work for me. I like knowing how deep and how warm the pool is before I jump in. I'm sure an argument could be made that writing is a creative pursuit, so the more creativity in the process the better. I understand this; but it's not for me.
Of course, things happen. Characters say things I wasn't expecting them to say which may start a new subplot or show me a new motive. That's great. Humourous exchanges or situations occur when I wasn't expecting them; that's great too. I don't want to think of myself as a mindless drone endlessly tapping away on the keyboard, but I do want to be in charge.
I outline. I do fairly extensive character biographies. I know who dies and whodunnit. I know why. I know why every suspect would have committed the crime. I know who likes who and who dislikes who. In short, I don't start writing until I know the road. I'm all for surprises and inspirations, but I like being able to know immediately that an idea, although fun or interesting, isn't going to help the plot or the subplots.
Who's in charge when you write? Is it you or is it the story?