Empathy. Something that most people seriously lack when creating business or academic presentations. But it's one of the most important things you can remember when you are developing a presentation for yourself. Walk a mile in another man's shoes, really. Or rather, never give a presentation that you wouldn't want to sit through yourself.
In the case of presentations, this issue has numerous outlets.
First of all, you absolutely need to identify your audience and understand their frame of reference before you write your speech. Are they techies capable of understanding your technical jargon, or are you trying to teach or educate your audience? Both options require very different techniques for delivery. Spew the techno-jargon on your unacquainted audience, and you will soon see the light—as audience members begin to surf the web on their iPhones. You have to speak to your audience—not condescending, but in a way that will keep their attention, while also getting the message to them.
Bombarding the target with dimmed lights, 12-point copy-filled slides, and boring content will surely not let your message be heard. Most people will give you 15 minutes of their attention before they tend to lose interest, but they will easily be able to tell right off the start of your presentation if even those 15 minutes are warranted. If you are not compelling, your message will be lost.
Put yourself in the eye of the audience. You know if your presentation is worth sitting through or not. If it is not in your mind, imagine what your audience will feel.