Humor is the way I always get the audience engaged. See, as a presenter, you have NO idea unless they give you feedback of some kind whether or not it's sinking in....but, if they laugh at a joke you make, you know that they heard you and they processed it enough to get the humor.
I wouldn't try to do "stand up comedy" if that's not the point of the presentation, but it's a good idea to use a joke or two during, say, a presentation that goes for over a half hour.
Visual aids are key, as well. At one point, I got a pointer that remotely controlled my computer so that I could use the laser and highlight parts of slides that were important, and so I could walk around on "stage" instead of standing still behind a podium.
For one, actually know your topic and know what you are going to say so you can look at the audience and actually communicate with your audience. Don't read off a paper, make eye contact. You could put up examples, appropriate jokes, video clips, ask questions to get the audience involved.