just dont think about the audience, channel them out so all you notice is the the music, the band, and the director. In university, they did things to get this out of you constantly. first we wrote down all the kinds of things that bother us when we perform, and it went from slamming doors, crying babies, talking, just people watchin etc and the we discussed this. Then the fun part, we did this to eachother in studio practices all the time. And I had a professor who when I did my juries, would jingle his keys off tempo and beat, and another who came and leaned on my shoulder. Just teach yourself to channel these things out of yourself and you'll be fine. I still get butterflys just before I hit the stage, but after that Im performaing and its fun time. Barisax((( is also spot on, breathing right, just like we do the rest of the time helps immensely

It's all in your head :) There's no getting around it, if you're not a confident player in front of people, it will feel awful the first number of times. That said ... play in front of an audience, any audience as much as possible. It will get easier the more you do it until it becomes a routine like any other. Even famous performers get 'butterflies', especially if they haven't performed live in some time. Others get them every time before they go on. I played for years in a live band every weekend until I got bored of it. Recently I started playing duets with a friend on guitar after not playing in public for a while, and I tell you, even though I'm in my late 30s, I was nervous all over again before I started to perform. Once you start, just channel into your music. Close your eyes if you have to. Once you start playing, just focus on your musicality and forget the audience. They're not going to change how you play, so why worry about them. My big break-through came when I decided to just 'go for it' and not worry about what people thought. I never turned back after that point and played better than ever. Remember, "it's all in your head". Good Luck!