Scott Berkun1 is a former Microsoft Engineer who severed ties with the mothership and went full-time public speaker some years back. His book, Confessions of a Public Speaker2 is sort of his manifesto on how he felt comfortable making that change and how he feels he's found success.
Scott acknowledges the simple fact that he feels comfortable giving away these secrets and hard earned knowledge simply because he knows that most people will never do the necessary work to become a truly great speaker. I know that I'm not apt to immediately. I feel that presentation is important, and I often present at regional Code Camp events and for WSU's Application Developer's group, something I began doing in part because I was tired of going to events and sitting through talks that I felt had little value either due to poor presentation, or just because I felt I knew more than the presenter.
More than that, I think that it's important to share information within our community. Between techniques and tools, we are certainly spoiled for choice, but without discussion and presentation, the majority of people developing software today have no chance to get expose to any idea that isn't backed by a marketing budget (this is a notable problem in the .NET and Java communities, but that's another post).
If you've done anything with public speaking in the past (and odds are you've taken a class at some time that did something with public speaking), you've no doubt heard much of this advice before. Practice, prepare more content than you think you need (but be prepared to cut content on the fly if necessary), practice, learn to harness your nervous energy, practice, show up early, etc. However, Berkun goes into a depth on this material that I'm not sure I've ever seen before.
He debunks common myths, like "people would rather die than speak in public," by showing where such myths came from and the inherent ridiculousness in such statements. He presents many cases from his own career of things not going well at all, like giving a presentation at the same time and across the hall from Linus Torvalds', who's crowd was overflowing into the hall, while he had less than a dozen sitting in his enormous conference hall.
While Berkun does stress that preparation is the key to making any public speaking gig succeed, it's the flexibility to deal with surprises that makes the best speakers as good as they are. Quick thinking doesn't trump preparation, but it's necessary sometimes to avert disaster.
One bit of advice that I'd like to share is what to do in that circumstance where no one shows up to hear you speak. Berkun suggests getting the crowd to move and sit near one another so that you can at least pretend the space is smaller than it truly is, while also making it easier to engage directly with the audience, perhaps turning it more into an informal directed conversation than a full-blown presentation with slides.
It is clear that Berkun was in technology, and still primarily speaks about tech, but despite his background, and the examples that he uses from his own career that refer to that, this is absolutely a public speaking book, and I think it's accessible to anyone who wants to improve their public speaking, even if you're not interested in turning it into a career.