Don't formulate arguments, etc. As a speaker, you need to pay attention to feedback from your audience. If a person in the audience seems distracted, bored, uninterested, focus on that person. Dress, hair style, body shape, etc., are also important to nonverbal communication. People are judged by their appearance.
Attractive people are more credible than unattractive people.
That is a fact of life, and there's no getting around it. If you want to be credible, stay in shape by exercising and maintaining a healthy diet. People who appear healthy and vigorous are more credible than weak, unhealthy people. That's why atheletes have so much credibility and make so much money in our society. Have you ever noticed the President, not just the current one, board Air Force One.