Are you 100% present in the moment when you give your presentation? 100% focused on your audience?
Or are you with your topic? Or with your own interests? Maybe already thinking about your next customer?
Are you thinking about the little time you have left to catch the train after the presentation? Or are you concerned about what the audience might be tweeting about you and your presentation?
Are you thinking about the next slide? Or focussed on not doing the wrong things with your hands?
The audience wills sense it when you aren’t completely present. Probably they won‘t be able to pinpoint their feeling, but they will feel it.
Conversely, if there’s nothing more important to you right now than your audience, they will sense that as well.
If you treat your audience with this kind of respect, they will treat you accordingly.