Zeno Racha wrote down some of his thoughts around public speaking. I've not given as much talks as he has but surely agree with everything in his post.

Having 10 years of experience on something is nice, but don’t wait for it to get started. The best speakers I've seen are not the ones who knows all the in’s and out’s about a certain topic. Here's the secret that nobody will tell you — the only requirement for giving a talk is passion. That’s it. No diploma, no famous project, no masters degree, no nothing. All you need is passion.