In a 2010 interview with the BBC, Alan Rickman talked about the importance of listening as an actor:
You only speak because you wish to respond to something you’ve heard. So the notion of an actor going away and looking at a speech they have in their bedroom alone at night is a complete nonsense to me. What you have to say is completely incidental. All I want to see from an actor is the intensity and accuracy of their listening. And then what you have to say will become automatic.