Most of what I learned about performing, or stage presence I learned by example. I was brought up surrounded by great 'performers' like the Friends of Fiddler's Green in Toronto, John Roberts and Tony Barrand, Louis Killen, etc. What these people did was really talk to their audiences as if the audience was a part of the whole. I really hate watching some so called performers today who simply play or sing their music on a stage without bothering to interact with their audience. Even if they are not perfect and awesome technically, I find myself bored if I'm not included in the performing relationship.
Of course, being a really good 'performer', or having really good stage presence, is not as simple as just talking to one's audience. However, I believe that is the basis on which to start. After a while, one improves. One thing that I find has helped me improve, even though it can be painful at times, is to have one's performance video taped. Watching yourself on tape is a sure way of teaching you what works and what doesn't.