I conduct workshops in Communication and Public Speaking - we go into depth about internal components and external technique.Ze Frank nails it in this short video. As always, he's straight up and quirky. His style probably doesn't appeal to some, although I can't imagine it.
This is the most important lesson about public speaking, or in fact, about life - that you have to be you. Emulation of others is a good start but ultimately, you have to let go and be yourself.