The very first time I did any serious public speaking was the final pitch at a Startup Weekend.
Preparing for it, I pretty much knew I was doing everything wrong (wrote out the whole talk word for word, was trying to memorize it, etc), but did it anyway, and... it was brutal. It took me 5 minutes to get through the first 45 seconds of my pitch, and during the Q&A the judges just said "No questions." I let my amazing team down, I embarrassed myself, and I embarrassed my employer... which was Startup Weekend itself!
(Un)luckily, one of my team was taking a video. A few days later, I finally brought myself to watch it.
Turns out... it wasn't as bad as I thought. Don't get me wrong - it was still bad. But it wasn't "an asteroid the size of Venus hit the Earth" bad. That made me feel a bit better. So I actively put myself in more places where I could speak, so I could practice and get better.
Fast forward a few years later to today: As I write this, I'm sitting on a hotel bed in Amsterdam. The Hyatt saw a talk I gave in the Philippines on Youtube, found a talk I gave at TEDxSeattle, then paid me (a lot) to fly me out to The Netherlands to give a talk at an internal sales conference they were hosting.
How times change.
But you know what? Before every talk I give, including this one, I get so nervous. Before everyone gets there, I like to sit in the chairs. Pretend to be out in the audience. I'll sit in three, four, five different spots if I can, and just watch the stage. Think about what it will be like for them to watch me. I try to get into the audience's head. Take a bunch of really deep breaths.
Then it's showtime. Performer mode turns on, auto-pilot gets engaged, and nothing can stop me.