I consider comfort with public speaking to be an important leadership skill. Leaders can not avoid being in front of groups, and they should strive to look comfortable there. Note that I didn't say they have to feel comfortable.
James Duncan Davidson is a photographer who has spent a lot of time photographing speakers, most notably for O'Reilly Media conferences. Being forced to watch both good and bad speakers has given him some insights into what works. I particularly liked this one: "Don't pace aimlessly. ... From the audience perspective, a speaker like this looks like a caged animal."
In public speaking, practice helps, but I've found that careful consideration of what works for others has been more help to me. James' article is well worth a read to help you avoid common mistakes.