There are two kinds of speakers.  The first kind – the far too frequent kind – is the kind that is afraid of the microphone, afraid of the audience, almost afraid of their own shadow.  (Yes, I am overstating this to make a point).  These speakers are simply too tentative.  They approach the microphone slowly, tentatively, almost as if they were saying:  “Is it okay if I speak to you now?  Are you sure it’s okay?  I’m not sure.  I’m a little uncertain about all this…”

The other kind strides to the podium, grabs the microphone, and says, in attitude and almost in words, “Listen up.  I’ve got something worthwhile to say; something that will be valuable for you to hear.  I promise not to waste your time.  So, let’s get going.”  This speaker oozes self-confidence.  This speaker is assertive, almost aggressive.  Yes, he or she can cross the line into arrogance.  But there is a self-confidence in this approach (and/or maybe it is not an approach; maybe it is close to attitude; maybe even “personality”) that grabs an audience by the throat and makes people want to listen.

This is the approach you want to aim for.

So, here is your model.  I remembered this from years ago, in an interview with Joaquin Phoenix, as he prepared to play the role of Johnny Cash in the movie Walk the Line.  Here’s a paragraph that describes it, taken from Cinema Review Production Notes:

From the minute he got the part, Phoenix began carrying a guitar. 
Phoenix knew if was going to get inside the soul of Johnny Cash, he would first have to get inside the soul of the musician. Cash’s stage mannerisms and guitar style had to become an organic part of Phoenix’s performance. Recalls Mangold: “One of the things John told me about whoever was going to play him was, ‘I just hope they know how to hold a guitar. You don’t hold it like it’s a baby and you’re frightened it’s going to break. You grab it by the neck.’ So I knew that Joaquin had to approach his guitar like it was something he had lived with all his life and that’s what he did.”

“You don’t hold it like it’s a baby.”  You grab it by the neck…  You own that guitar; you grab the microphone; you own that microphone…  And when you own that guitar, when you own that microphone, you have a shot at owning that audience.

(All of this assumes, of course, that have prepared your music/your speech well).

Was Johnny Cash arrogant?  Maybe.  But when he sang, he was certainly not tentative.  He was in his element.  And that’s what a good speaker is.  Not tentative, but in his element.