Begin challenging your assumptions. Your assumptions are the windows on the world. Scrub them off every once in awhile or the light won't come in.
A really great actor, in a lucky performance, can transform himself or herself. I've seen actors do that. But often it's a mechanical transformation, which isn't as interesting, and you've got to be careful how you go about something like that, I think.
The one thing I think I've noticed about shows that are supposed to be funny on television is that they've sort of become routinized, so there's an awful lot of mannerisms and joke lines that are sort of there to trigger laughter, rather than give actors a chance to play a moment.
I made my first stage appearance when I was 6 months old.