The key mistake made in preparing a presentation is in failing to identify purpose. “What is your objective, relative to this subject, in talking to this group, today?” The answer to that question can usefully be quantified in the elevator pitch but it is important to clarify that your material, the data, the “what”, is not the objective. Remember that this will vary for your particular audience. Your are not there to “cover everything”, to teach, to share, to tell or any other descriptive verb of generality, you are there for a purpose.
Clarifying that purpose is essential. The objective must be clear and it is not the material. The material represents a “what”, your purpose is determine a “so what” for the specific audience. This may take a long telephone call, an exchange of emails or a visit but it is essential in preparation that you have a clear understanding of the objective of your time in the spotlight. It may be that the organisers, instigators or seniors want you to “cover everything”, to teach, to share but it is only with a specific and identified purpose that you can begin planning. One can no more “visit Germany” without an objective than “cover Hirschsprung Disease”, “tell us about the Second Quarter results” or “talk about resuscitation.” To plan a presentation one must understand exactly the purpose. Where, precisely are you going?