Always get to the set or the location early, so that you can be all alone and draw your inspiration for the blocking and the setups in private and quiet. In one sense, it's about protecting yourself; in another sense, it's about always being open to surprise, even from the set, because there may be some detail that you hadn't noticed. I think this is crucial. There are many pictures that seem good in so many ways except one: They lack a sense of surprise, they've never left the page.