Give the message early in a talk so the audience will want to pay attention. If the message has value and relevance for them, they will follow the presentation. If the value is only delivered at the end, few will have travelled with the speaker and even fewer will be able to retrofit the information delivered. Give the message early on for a great presentation.
Very few presentations, save a comedic shaggy dog story, should end with a big reveal. The purpose of the presentation must be clear to the audience at the beginning and they must have investment in this. If not, it is a waste of time. The medical equivalent of a shaggy dog story the clinical case where all is not as it seems, is the greatest cliché. The audience will trust nothing that is said, spend their attention looking for subtle clues to something else and usually will be unable, at the end, even with direction, to re-construct the proper understanding in reverse.
Give the message early so that the audience can enjoy the travel of the presentation. They can relax with the message and engage in internal questioning knowing the ultimate aim of the piece. Rather like shepherding sheep, it is essential to minimise the early disruption and maintain flow towards a desired goal and not try to round everything up from confusion at the end. Give the message early to allow all thinking to be related to the end goal not diverse and distracted.
An intelligent audience will only pay attention to a presentation if they feel it is of value for them at the beginning. Crafting this value is the skill of a presenter and extends beyond lists or simply the presence of the audience. It is about understanding and learning not drama or suspense. However, that does not mean it has to be boring or of little value. Clearly one shouldn’t give everything away but if the message, the question, the value or the challenge is given early it engages the audience when they want to listen is highest and not seeks to gather them after they have been scattered.