is the key to successful presentation. Nothing will relax you more than knowing exactly what you want to say and having practiced saying it.
Doing stretching or breathing exercises before your talk can help you to reduce nervousness.
Make yourself familiar with the place where you will be speaking
It will be easier to speak to people who are not complete strangers.
Try to focus on the message and your audience not your own fears.
Imagine yourself speaking to your audience in a loud and clear voice.