I’ve attended roughly a gazillion presentations that began with an executive summary, or a brief statement along the lines of, “Here’s what I’m going to tell you.” 

Don’t do it.  If you have, stop now.  Promise me you’ll never do it again. 

Why?  Because if you begin with your conclusion, you invite disagreement.  Without the benefit of the logic of your argument, you’re simply asking your audience to take issue with what you’re saying.  That move derails your talk at the very beginning and means that a goodly percentage of the audience is no longer listening to you with anything like an open mind. 

What should you do instead?  Give a high-level teaser, a statement of purpose, something like, “Today I’m going to show you why a small change in your thinking can yield big profits down the road.” 

Or start with a brief story, and then give the high-level framing statement. 

Then lead your audience on the decision-making journey that will lead inevitably to your amazing conclusion.  The only reason to give a speech is to change the world.  That means changing the minds of your audience.  To do that, you have to respect their need to go through the decision-making process.  You don’t allow them to do that if you start at the conclusion. 

Never start with an executive summary.  You’re just asking for trouble.