If you ever find yourself invited onto such a set, accept the bowl of rice if it's offered. Mark the first clapboard with respect. Keep your eyes open for the unforeseen. Films, like rivers, will find their own channels; sometimes, in the half twilight between takes, the set will rearrange itself and give you a small, inexplicable gift: a look an actor never rehearsed, a wind that says precisely the right thing in the microphone, a face in the corner of the frame that makes the whole film a little truer.