How do convincing speakers vary their speech when they speak for different purposes and to different people?

When convincing people talk to others they use different tones and they go straight to the point. Instead of being serious the whole time they crack jokes to change the mood. They speak clearly and thoughtfully when asked a question. For example: person: Do you think that class is enjoying? Speaker: Yes, I do believe class is enjoying because you get a chance to meet different people and learn with them. Convincing people like to tell people all of the benefits of the decisions that people make.