Here's a tip from Bill Harley that came out of his Timpanogos workshop on Finding Your Authentic Self.
When you get on stage, or in front of your audience, first - find that place that is neutral for you, your home spot. Be aware of who you are as the storyteller/narrator. As the storyteller, you are NOT a character, unless you are telling the story AS a character, if so, then you must find the HOME of that character.
Relax, breathe, take a moment to find your home. This is what you will always come back to. Start at home. Fix a different stance, voice, facial expression for a character and go there...then come home. Go to another character, with another place...then come home. If two characters engage in a dialog, do NOT go home between each. Rather, make sure each is fixed in a different place, and go back and forth between each...then come home.
Home is your safe place. The place you alweays come back to. It's also the place where you can pause or take time to read your audience, or decide to make adjustments in your story.