Whenever people bring up the topic of humor to kick off a presentation, I am always reminded of a scene in the Woody Allen film "Bananas". Allen's character, Fielding Melish, dressed up like Fidel Castro, is at some Manhattan $500-a-plate function to raise funds for a fictional Central American republic. He is nervous, constantly adjusting his glasses, and his advisor tells him to simply start off with a joke. Melish approaches the podium to gaze out at a ballroom filled with tuxedos and sequined gowns. He starts out "I am reminded of the very humorous story of the farmer who had incestuous relations with all 5 of his daughters...". But for the sound of lower jaws slapping the floor, a deathly silence fills the room, as people stare, bug-eyed. Cut to the escape scene.
It's not THAT you start off with humor, it's what humor you start off with.
Personally, I think a good presentation is one that does the following:
1) Allows you to make as much eye contact with the audience as possible. If it feels like a personal conversation, people pay attention and stay engaged. If it feels like an impersonal lecture, they drift off, and the doodling begins. Consequently, your slides should really contain "prompts" that remind you of what you want to say, rather than content you are obliged to read. Few things are more disengaging than waiting for someone to finish reading aloud what you've already scanned through in a second.
2) Provides only as much content as is needed to elicit good focussed questions from the audience, and no more than that. Even if you have more content, save it for dessert. When an audience member gets to ask a good question, and the speaker can reply with "That's a good question", and answer it with cogent information that addresses the question, people are more apt to perceive the presentation as excellent and fulfilling, since it went beyond the actual presentation in a productive manner. Complimenting the audience doesn't hurt either. By contrast, a presentation that attempts to pack in too much, such that the speaker has to race through slides, declaring "We can skip that one....and that one", leaves the audience feeling confused and perceiving that the presenter had no particular organized message to get out.
3) The big picture. I mean this in the literal sense. My doctoral supervisor coached me to "Tell 'em what you're going to tell 'em, then TELL them, then tell 'em what you told 'em". Big circles-and-arrows diagrams, however, can permit people to more easily perceive the entire concept of what you're trying to convey. Not everybody, but certainly a great many, like to be able to see everything at once, and sometimes a visual "map" lets them do that. It gives you something you can point to in discussion, and fulfills the need for "prompts". Plus, it makes a great summary that people can use to re-convey to others what you told them.
4) Finally, given that public speaking is usually up in the top 10 of listed fears and phobias, nobody is waiting for you to screw up. They are all waiting for you to say somethng that interests them and makes them feel validated via their comprehension. The quicker you can get them to some degree of comprehension about something, the sooner they will begin to perceive the presentation as worth their while. Even if you think everyone in the room knows more about the topic than you do, reminding them of the validity of what they know will make you look good in their eyes.
One of the best presenters I've ever seen is intelligence and personality guru Robert Sternberg. His style is to always start with an anecdote and common sense example of what he will be talking about. Something that everybody in the room understands. Once everyone is convinced they will comprehend what is to follow, he then proceeds to present more detailed information that people can easily nest within, or link up to, the common sense example. Works like a charm.