One thing I would add though is regarding visuals. If you present with a slide deck make sure there is an absolute minimum of words on each slide. People will read every slide you put up, and while they are reading, they are not listening to you. The human brain just isn't modeled to be able to handle listening to one thing, while reading another.
Maybe your audience doesn't understand what you're trying to tell, maybe they already know.
Try to adapt on the fly.
I come into talks letting go of part of my ego, and come to see it just as my job to offer them something (intellectually) interesting. So upon sensing something's not working out, I might ask the audience a question to calibrate myself, quickly jettison it, or otherwise adjust.
(But not dropping all my ego. For some absurd reason, it helps to think of myself as enormously knowledgeable, and they're benefitting from this yapping... Sort of the opposite of the useful "I don't know a goddamn thing!" I prefer to feel when developing the talk in the first place. If someone in the audience happens to know what I know, like a previous speaker who touched upon what I'm saying, I often find myself including them in the talk somehow. If a significant fraction of the audience may know what I'm saying, I invite them to leave and take a pleasant break, so as not to be bored.)
Also, when thinking of part of my talk beforehand, I say the words out loud, which improves the fluency, and lets me hear more as an audience might. I did this recently on my way to work; saying and adjusting those words made them come out more fluently, because those parts of my cognitive system were already practiced.
