A little smile can go a long way.
Smiling is an almost universally positive communication behavior. People who smile are viewed as more persuasive, more likable, and more credible. They have better affinity with their audiences as presenters. And almost all of us could stand to smile more than we do.
Genuine smiles are called Duchenne smiles, named for the researcher who first identified the difference between real and fake smiles. When real, happy emotions are behind our smiles, we crinkle the muscles at the sides of our eyes. Sometimes we call these muscles the "crow's feet." (See the video below for more details.)