Most Keynote Speakers books say the same thing. The basics - make eye contact, speak clearly, don't pick your nose.
Professor Atkinson has written a compelling and very comprehensive book on how to present yourself as a guest speaker. Great speakers do more than the basics like eye contact, Atkinson goes deeper than this.
According to the professional speaker and leadership expert, you can use a number of techniques to keep the audience engaged.
Of course he still recommends eye contact, although he didn't have to spend an entire chapter on it. As a keynote speaker, I find the more I look at the audience, the more pressure there is for them to pay attention. If it is a disruptive seminar participant, I won't let them off the hook. I will stare at them as if to burn a hole through the chest.
For a guest speaker, a good stand up comedy technique is to engage the heckler in the crowd. If there is someone disrupting the seminar by talking to others or making gestures, then engage them in the conversation. Usually because there is tension in the room already, the audience will laugh at any interaction as a way to decrease potential conflict.
If you're a keynote speaker and speaking to a large crowd you need to convey extra enthusiasm. Fake it if you have to because ordinary levels flatten out over a distance (like the first two rows). A microphone amplifies your voice, not your enthusiasm.
Speak in a positive active voice. A passive voice makes you sound neutral, objective and detached, not good leadership qualities.
If you are a guest speaker and want to be remembered as great speakers are - do unexpected things to be extraordinary. Shake it up, find out what everyone else is speaking about and do the opposite.
Audiences demand something extraordinary from great keynote speakers.