The art of public speaking is the art of deciding what NOT to say.  The urge, when you combine expertise, adrenaline and an audience, is to tell that audience everything you know.  Unfortunately, long after the audience’s enthusiasm has waned, because they’re overloaded with information, you’ll still be going strong — because you love the subject! 

So you need to decide what the one vital idea is that you want to get across.  And one more thing:  your emotional attitude toward that idea. 

A great speech is composed of two things:  one interesting idea and the speaker’s emotional attitude toward that idea.  It’s that simple.  Don’t lard up your speech with caveats, asides, extras, nuances, added thoughts, one more thing, or anything else.  Stick to your well-honed subject and make your attitude clear and your audience will love you. 

Even more important, they’ll understand you.  And remember what you say.