Presentation creators have a tendency to want to build toward a surprising climax where unexpected results are revealed at the end. Don't to this, it doesn't work!
Slide presentations are inherently difficult to listen to. Some members of the audience leave early, some zone in and out, and some just miss things, no matter how good the presentation. So weaving a complicated narrative with unexpected twists and turns usually doesn't work (think about how many detective movies you've gone to, where despite months of script editing, you can't follow the plot).
There's an old saying about slide presentations, "Start out by telling the audience what you are going to tell them, tell them, and then tell them what you told them."
One of my favorite techniques is to present a visual roadmap diagram early in the talk that allows you to describe all the conceptual points concisely (see October 15, 2015 "tip"), clearing the way for the discussion of the individual measurements, methods, and uncertainties.
If the audience understands the entire story at the beginning, they'll get much more out of the entire talk.
