I have had the opportunity to work with Andy Lincoln a lot. He's got a remarkable process. He just has these ways of sinking into the scene and into character that are very physical. He'll make these sounds and these grunts and these moans... I don't know what it is that he's channeling! It lets you know it's okay for you to do that, too.
You want to go into scenes thinking not that you're the good guy or the bad guy, but that you've got a job to do. And I'm not talking about as an actor; I'm talking about as the character.