Communication to groups of people is harder than it seems.
It's difficult to craft a cogent message and hard to deliver it well. If there are fifty people in the audience a loosely organized message can be interpreted fifty different ways.
In addition, audiences process two sets of signals from speakers: verbal (what you say) and non-verbal (what you do). The video below helps explain.
Average speakers hunker and grip the lectern as if it's a life raft. Elite speakers work toward congruity, which means freeing up their body language. Top speakers do what they say and say what they do during the presentation.
Congruent communicators find a multitude of ways to "marry" their words to the gestures. Here are a few examples of congruency:
If you tell an audience that it's a pleasure to be with them, be sure to smile broadly and open your arms slightly.
If you're introducing three new ideas, hold up three fingers.
When telling a story, pantomime handshakes, head nods, expressions, and so on.
Being congruent with what you say and do will make you a more persuasive communicator because your body language will reinforce your verbal message message. This creates clarity and cuts down on misinterpretation.
The above video was recorded at a leadership conference in Chattanooga, Tennessee.