Eighteen minutes or less. That's the length of a riveting bedtime story; John F. Kennedy's inaugural speech; and the ultimate TED talk.

At 18 minutes, your pitch or presentation can deliver the impact, critical message, and enough information to influence your audience and leave a lasting impression. According to best-selling author and communication coach Carmine Gallo, creativity thrives under constraints, and a shorter presentation will elicit the strongest reaction from your audience. Just as we've learned to create intrigue with just enough information to capture our audience in 140 characters or less on Twitter, confining your information to the constraints of an 18-minute presentation will promote creativity and deliver loads of impact.

One of many researchers supporting this theory is Dr. Paul King at Texas Christian University who says that you aren't the only one who may experience anxiety about your speech or presentation: Your audience members feel anxiety, too. He calls this state "anxiety in listening performance." This anxiety is due to the fact that the more your listeners need to remember, the more pressure their brains take on, creating a backlog of information that causes the brain to fatigue and tune out. Limiting the length of your presentation will keep your audience engaged, and even on the edge of their seats if you do it right.

In preparation for his most recent book, Talk Like TED: The 9 Public-Speaking Secrets of the World's Top Minds, Gallo studied over 500 TED talks and interviewed many of the speakers, along with researchers in the fields of psychology and neuroscience. I found his book compelling and educational, and I'm now ready to shorten and reformat my speeches. In addition to the 18-minute rule, here are three takeaways (I'm already using one of Gallo's rules here) that I hope you'll find helpful in preparing your next big talk.

Use the rule of three.

The human mind can typically hold only about three chunks of information in the short-term, or working, memory. As you add more items to the list, the average person retains less and less of your information. If you have as many as eight points of information, the majority of your audience will forget the entire sequence. Gallo suggests creating an outline for your presentation using three stories, much like Major Carter did in her TED talk, "Greening the Ghetto." Tie your stories together in a central theme using three examples and three lessons that reinforce the theme, just as Carter did in her popular talk.

Gallo suggests creating what he calls a "message map" to help you pitch anything in as little as 15 seconds or to shape the framework for your 18-minute presentation. Your visual map will include a powerful headline, three key messages, and three bullet points highlighting the stories or facts that will support each message.

Paint a mental picture with multi-sensory experiences.

Remember, the brain won't pay attention to the boring stuff. Add components to your presentation that touch a number of the senses. Gallo suggests exposing your audience to mesmerizing images, captivating videos, intriguing props, beautiful words, and more than one voice to bring your story to life. He also warns to steer clear of the traditional PowerPoint display, chock full of words. He cites Brené Brown's presentation, "The Power of Vulnerability," as a powerful example of using imagery to replace words. But your words need to paint a picture as well; don't rely on visuals alone.

Lighten up.

Gallo uses the most popular TED talk ever to demonstrate the power of humor and novelty, both of which the brain loves. While creativity expert Sir Ken Robinson spoke about how schools kill creativity, a topic unlikely to attract more than 25 million views, he succeeded by lowering the audience's defenses with his novel approach to the controversial topic of education reform.

To lighten it up, relate anecdotal information about yourself or someone you know, light-hearted observations about your work or industry, or personal stories to elicit laughs from your audience.  Analogies and metaphors will not only help to explain complex topics and ideas but can bring a smile to your listener's face as well. Even a silly, yet relevant, YouTube video is an effective way to bring humor into a presentation, and will take the pressure off of you to be funny.