One of the most valuable things that has happened to me regarding public speaking was watching a talk that I gave. I said 'um' way more than I perceived I did. It was painful to watch. I now do everything in my power not to utter it. Instead, I simply pause. My talks have much improved as a result.

If I were to become a politician, I would watch my own speeches whenever possible.

IMO another important thing to do is to tell a story. It is so much easier to talk about something when you frame it in the context of a story.

I get a bit nervous before a talk, but I've learned to prepare a bit more, and to care a lot less. The audience mostly just wants to relax and learn about something. If you do your best to explain something without boring them, you'll be alright.

In a couple of weeks, I am slated to give a talk to the Physics Department of my alma mater. As a student, I used to attend these talks religiously. It will be interesting to be on the other side of the podium, and to present to the faculty that taught me.