This goes right up there with “never move  your hands when speaking” when it comes to bad presentation advice. If you don’t believe me, take this little test:
Quick: How many emergency exit doors are there on a 737 airplane? Any time I ask this to a group of presentation trainees, I get answers ranging from 2 to 12. Everyone has a different answer. My point is that anyone who travels has been told exactly how many exit doors there are dozens or even hundreds of times and yet we still don’t remember (confession: I have no idea how many exit doors there are) We don’t remember how many doors there are on the plane because when we are being presented with this information it is done in such a boring and perfunctory manner, typically right after we are being told how to fasten a seat belt, that we aren’t listening, therefore we don’t remember—no matter how many times we hear it.

And yet, we all have some presentations permanently etched into our memory, even though the presenter said something once, but in a memorable way. I can still remember my 5th Grade teacher, Mrs. Evans, telling me, “young man, you are going to have to hold this door for me, whether you like it or not.”  Yet she only said it once, yet it stuck because it was frightening!
Here is the fundamental insight: it doesn’t matter if you say something 3 times or 300 times. If you say it in a boring and unmemorable manner, no one will ever remember it. If you say something once in a memorable, visual, emotional, specific, relevant way, people will remember what you said minutes, hours, days, even years later.
The goal of telling them what you’re going to tell them, telling them, and then telling them what you told them is to get your audience to remember your messages. This is an excellent goal and I applaud you for focusing on this particular objective. But at the tactical level, this method isn’t very effective. A far more effective technique is to package your messages with interesting and memorable stories, case studies and examples and to deliver them with passion and feeling.
There is one scenario when it does make sense to do the tell them what you are going to say, tell em, tell ‘em what you told’ em technique. This is when you are in a classroom teaching setting and all of your students are writing down detailed notes in preparation for a test on the subject matter later. In this case, your organization will make it easier for the note taker to see the outline and structure when reading the notes later.
But your new business prospect is not going to write down notes on your pitch presentation—and if he/she does, it won’t be studied later. Your boss isn’t going to write down notes of what you say at the Monday morning staff meeting. Sales people listening to you at the annual sales meeting will not write down what you say. You have to realize that most people in the world in non-academic settings are not going to be writing down everything you say and study it later. Therefore there is a lot more pressure on you to present your information in a way that is easily digestible, understandable and memorable for your audience.
So spend less time focusing on telegraphing the outline of your presentation to your audience and spend more time simply being interesting.