Body Language
Why is it that some speakers hold your attention with no effort at all while others made you work to stay awake? Some make you feel like the most important person in the audience, while others look like they wish they were anyplace else but here.
Unfortunately, many people feel that speaking in public is like walking barefoot on hot coals. You can actually see their discomfort. They can't stand still. They're constantly shifting their balance from one foot to the other, like marching in place.
For others, standing in front of an audience is like facing a firing squad. They plant themselves on a spot and freeze, afraid to move an inch or they might get shot. Or they hide behind the lectern or podium, afraid to come out from behind its protective shield to get closer to their listeners.
Then there are those who seem perfectly comfortable, but they can't figure out where to put their hands. They lean on the podium, fiddle with their glasses, juggle their slide pointer, run their hands through their hair, hitch up their slacks, scratch an itch, cough, blink, and display other mannerisms which only distract you from hearing what they're saying.