After being on both the giving and receiving end of plenty of presentations, I now realize there's one golden rule which applies to all of them:
Entertain your audience.
Every slide of your presentation should serve this fundamental vision statement. Is it entertaining? I don't mean each slide has to contain a wacky joke of some kind. Every slide should provoke a reaction from the audience -- be it controversial, unexpected, amusing, or a meditative Zen koan. Prod your audience. Do this not only to keep them awake, but to engage their brains. Deliver a series of short, sharp shocks that jolt your audience into a heightened state of engagement.
Once your audience has engaged with your presentation, that's when you trick them into learning. The very best presentations entertain and educate-- the common portmanteau is edutainment. The archetypal example of edutainment is Sesame Street.