One can always try to "just do it", or try "chemicals", but if you look to the evolutionary history of humans, and how it has impacted our physiology, you will have more tools to work with than just "will power", or pretending the audience is friendly.

Two aspects: First: human beings are highly adaptable, and can get used to just about anything. Second, in our evolutionary stage in the recent past, when we were often the prey, our systems evolved to inject substantial amounts of adrenaline into our bloodstreams, to provide energy, to sensitize our fear-awareness mechanisms, and to shut down parts of our brains that we do not need too much at that moment. Legs trembling uncontrolably, hands shaking, hyperventilating, and narrowed mental focus are all the direct result. They are physical processes, not mental attitudes or moral weaknesses, or lack of preparedness. They are getting you ready for "fight or flight", because you have been thrown into an unusual situation, where less evolved parts of your brain are imagining that you are exposed to some danger. While the actual danger may only be the risk of looking dumb, your brain still reacts the same as if it is the danger of being eaten by a saber-tooth tiger.

So, how does one burn off excess adrenaline? Physical movement. Swing your arms. Walk around the stage. Pretend you are swinging a golf club. If you don'rt burn off enough, you'll still feel "nervous". If you burn off too much, you might take a fine edge off of your performance.

With time, as your presence on the stage becomes less alien, and you feel less and less like prey, you will find that your system generates less adrenaline, and performing will become easier. This is like training in the military, or the police, where the same movements are run through over and over, to make them feel less alien. You will still always be nervous, but it will be at a manageable, and even helpful level.

Forget that crap about drugs and booze - you already have enough of a chemical soup churning around in your own system.

Learn about your brain.

Use it.