It's a bit of a mix, I think. I have this idea for 'what's going to happen'. Obviously, that's affected by characterisation issues. For me, writing a story is like building a house. You have a plan, but you realise you've cut that joist too short, and you have to cut a new one; you can't get that variety of tile and have to go with something else. I think that you, Gilly, go with 'content defines form'. I go with 'form defines content'. :-)

To go back to Hazard, I was going to have Alicia just as affected by the sentinel attraction thing as Jim, but I soon realised that it wouldn't work. The scene where Jim licks her hand was originally intended as a way for Alicia to drug him and put Jim even more off his game. However, no. Alicia is a survivor, and she can't do the things that I want her to do if she's swanning around in an uncontrolled puddle of lust. So, I changed the emphasis. So yes, things are character based, but it's more me thinking, 'what sort of person will do the things I want to have happen here' rather than having the character determine the flow of action.