Yup, I've been thinking about how to deliver successful public speeches recently, and I think there are 4 keys to delivering a good speech:
1. Practice.
Try to learn what you're going to say so well that the only thing you actually have to think about "on the spot" is how you deliver it.
2. Charisma
I could say a lot about this, but basically, the theory is that when good public speakers get up on stage, you're not seeing them. You are seeing a persona that they have switched on.
Here's a long but very interesting video about using charisma in everyday life:
3. Body language.
This is something I don't think about enough, but so much of what we're going on privately in our heads is betrayed by our gestures.
Here's another video worth watching:
4. When you are inexperienced, you don't have a "public speaking voice or character" to fall back on. So you may want to think about borrowing someone else's.
For example, maybe you like the way Barrack Obama confidently and reassuringly addresses the press.
Watch a bunch of videos of him doing that: Study the gestures he makes, the pauses, the way he stresses certain words and syllables.
When you forget and what he's saying and focus in on how he's saying it, you'll realize this is not normal or natural speech, but a tailored style of communicating that is so effective that he's now President.
Finally, my last tip would be to understand that fear and nerves are natural.
It's not natural for you to be in a room full of people staring at you, unless you do it for a living.
When your stomach starts churning or you get all jittery and nervous, what's actually happening is your body is picking up on the "danger" of the situation: What if you screw up? What if people laugh at you?
That danger puts your body into "fight or flight" mode - a biological defense mechanism that has helped humans escape dangerous situations for thousands of years.
Accepting and understanding why that's happening is the first step to overcome it. You have to rationalize with your mind: "I do know what I'm going to say, no-one is going to laugh at me, I'm only on for 5 minutes - other public speakers talk for hours..."
These are the kind of thoughts that will help you "talk your body out of fight or flight mode", which is when you start to relax and have fun!