Someone in another thread someone mentioned the line in Shakespeare in Love from the actor playing the nurse in Romeo and Juliet when asked what the play was about. "Well...it's about this nurse..."

That actor has actually hit the nail on the head. You will give a truly well-rounded performance if you act from the point of view of the character you're playing. Of course we say that all the time. It's the foundation of realism. But we don't often discuss it in such a context.

The fact that many actors seem to forget about when they're given an Ensemble part, that is, something with a few or several lines and/or silent bits, this character 's world revolves around themselves, just as it does for all of us. To that character, the play is indeed about himself or herself.

Too often I see actors, particularly in community theatre, though also in University on occasions where the person has not yet had a great deal of experience and the director doesn't pay attention, donning their characters as though they were a coat. Sometimes it's not as noticable. However, were the actor playing a character with a visible impairment or deformity, the problem would likely be highly noticable.

Though I doubt an actor without much experience, or who was prone to this sort of thing, would be playing the role unless the director had few options or perhaps had squirrels living in his skull, I'll use Richard III as an easily recognizable example.

The actor walks out on stage, in his normal stride. As his whole body reaches the light, then and only then does he 'deform' himself, clawing up the hand and hunching over.

There is no real 'trick' involved, it's just a matter of training oneself. "My character is X. He works at X sort of job, and is always tired. He is easily annoyed by the antics of his son-in-law, X, and has an incredible urge to refer to him as 'meathead.' So, he would carry himself in a way that reflects that."

Coat-Character is an easy habit to fall into if one isn't careful, especially in roles where the change isn't so obvious. I caught myself doing it during a run of one-acts, and quickly took steps to make sure that I was fully in character from the moment I lifted my foot to take that first step onto the stage. I haven't been sorry.

Hope this has been informative! If not, just throw things. 

Wow, you sure do raise a lot of good issues in one post!

I'm the one that told the Shakespeare in Love story, by the way.  This is part of why I told the story; I do think that way.  As I may have said elsewhere, right now I'm in a production of The Man Who Came To Dinner that is -- for me -- all about Professor Metz.  I can't really approach it any other way as an actor.  Nobody is a supporting character in his own life.

On the other hand, I think there's some danger in presenting the issue to an inexperienced actor in this way.  If we tell the actor to approch the play as being about her, what happens to our credibility as directors when we later tell her to stop pulling focus?  As I said, I think it's a good technique and I use it, but I think we need to emphasize the distinction between preparation and performance. 

More in a separate post.

I had more to say, but work intervened, and I forgot half of it and the other half is pretty much off topic.  So I'll just tell a semi-on-topic joke:

Eager young student to John Barrymore:  Sir, do you think that Romeo and Juliet consummated their relationship?

Barrymore:  In the Chicago company they did.