Don't say stupid things. If you haven't anything worth saying, let the music speak. The audience is a whole. Keep this in mind as you perform. They become of one mind as you take them places.
Music is a right-brain function.
Listen to the sounds of the music. It comes down to focusing your mind. Get control of your mind. You're much better off focusing on the music than on being nervous, which just feeds itself. It's not a matter of not being nervous, but of how to perform well whether or not you're nervous.