Firstly, do plenty of practice. Remember the 5 Ps: Prior Practice Prevents Poor Performance. You do not need to practice in front of a mirror. However, you do need to see yourself up in front of the actual or imagined audience.
You should précis your points down to point form and have them on a small piece of paper. If you do need to have the whole thing written out, place it on the lectern and only look at it when you need to IN SILENCE.
Practice the voice changes and the gestures as well, in your head, if not in fact.
When you do speak on the real occasion, go to the toilet before you speak and drink a glass of water to keep the voice lubricated. Focus on what you are saying the whole time. As soon as you become “self conscious” you will start to be distracted and then you could become nervous, wondering what they are thinking of you. All your energy needs to be on what you are communicating out, not what you imagine they are thinking about you!
(I know that’s easier said than done.)
If you really believe what you are saying and speak with a mix of logic and emotion, connecting with the audience, even cracking an occasional joke, they will love it.
Lastly, breathe deeply to calm your nerves. It allows your voice to come up and you will have more pauses when you give yourself permission to breathe deeply. (Don’t over do the deep breathing or you could hyperventilate)
So, remember, nerves are normal. Harness them. Connect with your audience and practice, frequently.