The secret of public speaking is. . . listening. 

Wait a minute, you say, how can I listen?  Surely the act of public speaking creates an expectation that I’ll be doing most of the talking? 

Well, sure.  But you should know your speech so well that you can devote a chunk of your brain to listening to the audience — even if it’s not speaking.

Because, even if it’s not speaking, it is emoting back, it is squirming in its chairs, or nodding off, or leaning forward attentively, or whispering to its neighbors, or one of a thousand kinds of non-verbal communication that you need to listen to.

Why? 

Two reasons.  First of all, the only reason to give a speech is to change the world, and that means the audience in front of you, and you can’t change the audience in front of you without listening to them — without understanding them better than they understand themselves.  You’ve got to know where they are in the journey of the speech you’re taking them on.  You’ve got to know when they’re not getting it, and you have to slow down, or when they’re ready for the payoff.  And so on.   

Second, it will make you more charismatic.  Charisma is emotional expressiveness, and attentiveness.  If the audience thinks you’re paying attention to it, that’s flattering…and charismatic.

So, listen to your audience.  It’s even more important than speaking.