Any presentation is prepared to cover all the three aspects, viz., introduction, body and closing. You start with a greeting and introduce the topic. You should get the audience hooked by telling a story or illustration, referring to a disturbing event or information, asking a rhetorical question or telling something that at once arouses interest.
In introduction, the speaker tells the audience what he or she is going to present and how it would benefit them. Moving to the body of the presentation, the speaker covers all the main points of the topic, puts in supporting material and ensures a comprehensive coverage. The closing or conclusion quickly sums up the main points and emphatically makes the final point.
Preparation ensures that all these aspects of presentation are brought out in a clear, cohesive and well-organized manner. Preparation also includes choice of visual aids and ensuring their availability in proper working condition at the time of presentation.
Practice, it is said, makes a man perfect. Practice here means rehearsal of the presentation. You make sure that vocal, verbal and visual aspects are in sync to create the desired impact. You ensure that the presentation can be completed within the time allotted, even after providing for some interruptions to seek clarifications. By practice, the speaker ensures that nothing is taken for granted.