Via The Charisma Myth: How Anyone Can Master the Art and Science of Personal Magnetism:

1. Lower the intonation of your voice at the end of your sentences.
2. Reduce how quickly and how often you nod.
3. Pause for two full seconds before you speak.

Why do these work?

I’ve posted a number of times on the power of your voice. You can predict who will be elected president by how deep their voice is.

Men with deeper voices are more attractive and women are more likely to remember what they say.

Pausing has been shown to make you more persuasive.

The book does a good job of explaining why controlling nodding is key:

Can you imagine James Bond fidgeting? How about tugging at his clothing, bobbing his head, or twitching his shoulders? How about hemming and hawing before he speaks? Of course not. Bond is the quintessential cool, calm, and collected character. He epitomizes confidence.

This kind of high-status, high-confidence body language is characterized by how few movements are made. Composed people exhibit a level of stillness, which is sometimes described as poise. They avoid extraneous, superfluous gestures such as fidgeting with their clothes, their hair, or their faces, incessantly nodding their heads, or saying “um” before sentences.

bond is a great image for this.  imagining him saying um is hilarious!

That could be a comedy bit. When we need to keep calm, think James Bond. 

This comes to mind.