When you’ve experienced a great speaker, you just know it.

They kept your attention in a vise grip. It feels like their presentation was over all too soon, even if in fact it lasted two hours. And long after the event, their words still echo in your brain.

Three well-known speakers in particular have this effect on me: Tony Robbins, Mitch Joel, and Nancy Duarte.

After watching them speak at various events, I’ve identified three qualities they have in common, that set them apart and make them powerful, memorable speakers.

1. They have exceptional depth of knowledge and insight.

Great speakers have such expertise of their subject matter, that they couldn’t possibly share everything they know in a presentation.

For example, Tony Robbins, who’s a motivational speaker, self-help guru, and financial expert, knows more than anyone what it’s like to overcome all the disadvantages life can throw at you and still succeed. He had a difficult, impoverished childhood and didn’t attend college. But beyond having life experience, he also received training from the best mentors: Jim Rohn and Neuro-Linguistic Programming co-founder John Grinder.

Nancy Duarte is a best-selling author and CEO of Duarte Design, one of the biggest design firms in Silicon Valley. She has received several awards, including Mountain View Woman of the Year, Microsoft’s MVP Award, USM’s Entrepreneur of the Year, and Communicator of the Year in 2007 and 2008.

For his part, Mitch Joel has been called the “Rock Star of Digital Marketing” and “one of North America’s leading digital visionaries” by Marketing Magazine. In 2006, he was named one of the most influential authorities on blog marketing in the world, and in May 2009 he was included in the Top 40 under 40 in Canada.

In other words, these three know their stuff!

But in addition to being experts of their subject matter, they’re also students and masters of communication. They know how to transmit their knowledge to their audience effectively through the structure of their presentation, their choice of words, their visuals, and their movement on the stage.

“Enlist some help. If you don’t think that your presentation skills are up to snuff, please get some help,” Joel advises, “Toastmasters is great, a local presentation skills coach, or even a local stand-up comedian can best help you massage the content and build proper presentation skills. You will be amazed at what you can learn in just a couple of hours.”

2. They’re genuinely passionate and excited about their content.

“Don’t ever speak publicly about anything that you’re not passionate about and that you don’t actually believe you have something truly unique to deliver. Don’t get roped into talking about something that you don’t really have passion for, and don’t get roped into something you don’t have expertise in,” Robbins says.

It’s not enough to know what you’re talking about; you also have to have absolute conviction that what you’re presenting can help the audience and potentially change their lives for the better.

3. They respect the audience.

For great communicators, it’s all about the audience.

“The number one thing is to be audience-centric,” Duarte says, “To take the time to think through who the audience is and develop all your material from a place of empathy toward them…. By flipping that paradigm to an audience-centric approach, your material will resonate and the audience can feel a deeper connection to you and your material.”

This sums up what makes these speakers great. They truly care about the audience and have a genuine desire to serve them.

You Can Be A Better, If Not Great, Speaker, Too

If you want to be a better, or even a great, speaker, you can begin by watching powerful speakers in action, starting with the three below: