How we change what others think, feel, believe and do
To build confidence and skill in public speaking, whilst practice and doing it is important, you can do a surprising amount and develop your ability with this internal, mental exercise.
Start by taking a topic which you like and know well. It can be anything from a TV show you like to the story of your childhood. Now imagine you are talking about this topic to a group of friends. Easy, huh?
Now make it a bit more difficult, for example putting it in a hall with a low stage and you standing on it, with the same friends there.
Then maybe add a few other people you know. And perhaps a smiling and safe stranger or two (such as a friendly old couple). Gradually increase the size of the audience at the speed of how comfortable you grow in doing this. To do this, of course, you need to notice how you are just feeling more confident with the idea.
You can also then increase the 'difficulty' of the subject, perhaps going back to a smaller audience at first. In doing this you don't actually have to think exactly what you are saying. Just visualize that you are saying something, and that the audience are paying attention and smiling.
You can even take this to extremes, imagining being a rocket scientist, talking to a stadium full of astounded people.
This process works first by doing it in the mind rather than in reality, where you have control of all variables and can do 'magical' things like make the audience disappear or become out of focus. The principle of progression then enables you to gain comfort one small step at a time. Scariness comes in big leaps, so this can be handled by progressive increments.
A helpful extension to this method if you find it uncomfortable at any time, is to imagine yourself at the side of the stage, seeing yourself talking comfortably. Or even sit in the audience and see how impressive and confident you look.
And the big