The first article - "The Presentation of Self in Everyday Life" - had many interesting ideas, but I am not convinced of how true they are in real life and how often they really play out. While I do agree that people care about how they appear to others and the relative relationship that everyone has to everyone else does exist, I do not agree with the idea that this is the overriding universal constant truth of all human interact. In some instances, yes, but I think a lot less energy goes into this type of superficial interaction than Goffman implies. I don't feel that life is just one big game of chess.
I was more inclined to agree with the points of "An Actor Prepares." What I really found interesting (and that in my experience seem to ring true) was the notions of what a successful performance - or rather presentation - is and how to get there. Though I have little acting experience, as I was reading it, I was reminded of my martial arts experiences. The idea of not thinking, but just being, just being in the moment (or in the character) so that what you are doing is real and is true is what really makes a performance successful, both on a personal level and for the audience. But before that stage can be reached, constant practice and continual evolution and growth must occur. The "act" becomes engrained so that you do not have to think about what you are doing -- and in fact you cannot think about what you are doing, it is just intuitive, you are just focused and present in the moment. I have experienced this in doing martial arts forms before and at these moments when I am not thinking about anything but am just completely focused, but not at anything in particular --- I am most successful at these moments.
I also find that there is truth in the immediacy and urgency of the moment that was expressed in "The Grotowski Sourcebook." When you are really experiencing something, you do not think about what you should do, you just react and feel and act and there is no way to anticipate ahead of time what will happen or be felt. I think if this kind of immediacy can be transferred to acting than it will make it much more "real" and less like an "act."