Any good presentation has 3 basic parts.
An introduction that captures the audience's attention and tells them what the talk will cover.
The body, which is the core of the presentation.
A summary/closing that reviews the main points, tells the audience what action the speaker wants them to take, and relates back to the introduction.
A talk should flow from one part to the next. Points or steps within the body should be covered in logical order with smooth transitions from one point to another.
It is important to get the audience's attention quickly in the introduction of a talk. Here are four examples of ways to get attention.
Yell....."Fire in the Kitchen!" - this is very effective but should be used sparingly.
Question....."Have you ever thought about how airplanes fly?"
Quote..... Shakespeare once said, "To be or not to be, that is the question"
Surprising fact....."Car accidents are the number one killer of people 16-20"
Make sure you cite sources of factual information where appropriate.
Other ways to gain your audience's attention is through the telling of a funny joke or story or relating a personal experience.
One final note is that speakers should use humor and select jokes cautiously because if the audience is offended there is a potential to lose them permanently.