3 ideas
Before preparing a talk, define the specific action or change you want from the audience, then work backwards to select only material that drives toward it. The organizing question is not 'what do I want to say?' but 'what do I want to happen?' — everything that doesn't serve that result gets cut.
Every act of communication is governed by the relationship between who you are, who is listening, and what you want to achieve, and a message must be adjusted whenever any of the three changes. A presentation that ignores the audience's existing concerns and frame of reference fails no matter how polished the speaker is.
Audiences respond to a speaker's genuine conviction and natural personal style far more than to memorized techniques or rhetorical polish, and visible discomfort with a 'performance' mode undermines credibility. The goal of training is not to mask your natural self but to project it more fully and confidently.