In animation, the eyes move first and the body follows. Attention usually leads action in real life too.

Movement reads as alive when it starts with looking. A character who turns their head before their shoulders seems to have decided something, while one who moves all at once seems pushed. The same order shows up in people: attention goes somewhere first, and the body catches up a moment later. Where someone is looking is a reliable preview of what they are about to do.

Watch a few seconds of someone walking into a room and note what their eyes do before anything else moves. In a conversation, notice where your own attention has already gone, because it is probably announcing your next move.