A major fault of presentations that is seldom addressed is the tendency for most presenters to create presentations that are wide instead of deep. Let me explain.
If you're presenting something, anything, that usually means (I hope) you know a great deal about the subject. To use a personal example, I've been playing volleyball for 13 years, coaching for nearly 10. I know a great deal about the game, but often the players I'm coaching don't. I could sit them down for hours and hours and teach them the game of volleyball. Problem is, there's not one person in this world that wants to listen to me talk hours on end about volleyball. I'm a (self-proclaimed) interesting guy, but not THAT interesting. Even if they were THAT interested (not likely), that's simply too much information to consume in one sitting. Much of the information will go in one ear and out the other to make room for other, more recent information.
The same thing happens when a presentation is too wide. A "wide" presentation is one that covers a vast amount of information without going into much detail on any one point. It's the curse of knowledge. The presenter often knows far more than the audience, since it's their job to teach/enlighten them. Unfortunately, without a concentrated effort to reduce and simplify the presentation to a few key points, a presentation can become too wide, thus teaching them a little about a lot, instead of a lot about a little. Since the time constraint never changes (you're given 40 minutes to speak), the more "points" you add to the presentation, the less time you have to elaborate on those points. The audience gets a shallow view of many points, resulting in few, if any, being recalled. Thus, both the audience and the presenter's time has been wasted.
Instead, narrow your presentation focus to a few key points. Go a little deeper to explain each of those points in a way that the audience will be able to keep up with, understand, and retain. Even if your audience doesn't remember every little detail, you have a much better chance at having them retain your most important takeaways.
