I've always felt it's the directors purview to say what; it's the actor's purview to say how. It's not good for an actor to have the big picture in mind - it bollocks you up. An actor's purview is the tiny little... We measure our performance in seconds.
Every scene has two people who want two different things, so there's conflict in every scene. You've got to duke it out, and you've got to get the other person to change his or her mind and do it your way.