How do I get information to prepare a speech?

So you have to prepare a presentation.  Where do you find the information for your speech?

Surprisingly, much of what you need is already in your subconscious and experiences.

Why enter a speaking competition?

Why on earth would you put yourself through the stress of a speaking competition?

What makes a person put their hand up and have a go?  Do you need a massive ego?  Do you have to be a super extrovert who loves the limelight?

What's the point of it all?