These four simple rules will help ensure that your audience sits up and pays attention.

It takes an audience about 15 seconds (at most) to decide whether your presentation is worth their attention. Fritter away those fifteen seconds and your audience will either mentally check out or pull out their phones to start texting.

Here's how to begin a presentation so that your audience really sits up and takes notice.

1. Have somebody else introduce you.

Don't waste time explaining who you are and why you're there. Write a short (100 word) bio and a short statement (50 words) of what you'll be talking about. If you were invited to speak, have whoever invited you read this information to the audience. If you called the meeting yourself, put that information in the invite.

2. Do not tell a "warm-up" joke.

I have no idea how the "warm-up joke" became part of conventional business wisdom. Most of the time, the "joke" consists a weak attempt at situational humor (like "why are these meetings always on Monday?") that merely communicates that you're nervous and unsure of yourself. The rest of the time, the "joke" is a long story with an obvious punch line that tries everyone's patience.

3. Do not begin with "background."

Many presentations begin with a corporate background that's intended to build credibility. (Example: "Our company has 100 years of expertise!") The problem here is that at the start of a presentation nobody cares about your company. You're asking them to translate your background information into something that's meaningful to them and their business. Why should they bother?

4. Open with a startling and relevant fact.

To get an audience focused on what you're going to tell them, you must first break through the "mental noise" that causes their attention to waver. This is best accomplished by a slide showing a fact that is new to the audience and important enough to capture their attention. Build the rest of your presentation to answer the business questions that this initial fact has raised in their minds.

Here are two samples presentations to help explain these points:

BAD:

"Hi, I'm John Doe from Acme and I've been working in the widget industry for 20 years. And boy, has it been an exiting time (just kidding!) Acme is the industry leader in widgets with over a million satisfied customers!! I'm here today to talk to you about how we can help you save big money on your purchases of high quality widgets."

BETTER:

"Yes, one million dollars." (Pause.) "That's how much money you're losing every year because of widget failure. Fortunately, there IS a better way and I'm going to explain how you can easily save that money rather than waste it."

Needless to say, the slides in the above example are simplistic. The "better" example could probably be made more visually rich, perhaps with an illustration of money going down a drain (along with the $1m).

What's important here is that you realize why the surprising and relevant first slide is far more likely to capture the audience's attention than the typical rambling intro.

Please note that the "startling and relevant" fact need not be an attempt to generate fear.  The fact could just as easily be about possible opportunity, the achievement of a long held goal, or something else that inspires. As long as it's surprising and relevant, the audience will listen.