The character of Macbeth changes very dramatically throughout the play. At the beginning of the play - Act 1, Scene 7, Macbeth struggles with his conscience, over whether or not to go through with the murder of Duncan. His character at this stage is noble and brave, and doesn't want to look like a 'coward' to his wife, so he is quite easily persuaded to do what Lady Macbeth wants. At this stage I would want the actor playing Macbeth to try and reason with his wife, and be quite defensive about it. I also would want him to be a bit unsure and to be more and more persuaded so that by the end of the scene he should look quite convinced yet slightly worried. The character at the end of the play, in Act 5, scene 3, is very different to the character at the beginning. He is more sure and confident, now with nothing to lose and nothing to live for except the power of the crown.
He is filled with ill-deserved confidence because of the prophecies. I want the actor to be in control, and totally confident. He should also be unafraid, show no fear, and be annoyed by the amount of fear shown by the other characters in the scene.
"I dare do all that may become a man, who dares more is none"
At this point, Macbeth is trying to explain and back-up why he doesn't want to kill the king. I think he's saying that he does all that makes him a man, if he goes too far, he's no longer a man. I think the actor should be looking directly at Lady Macbeth, right into her eyes to show that he means what he says and that he's speaking from the heart.