Practice your talk at least twice. The first time I practice a talk, I fumble for how to word things, and I have dead time trying to figure out what and when I should say something. The second time through, everything flows better, which gives me the confidence for the actual talk.
I agree with what he says about slide design, but I think practicing your talk is the most important thing. I always give extemporaneous talks. Practicing doesn't provide you with a verbatim script, but it does provide you with certain ready-made phrases you can pull from your mind, along with the intuition of "I just said X, I need to make sure I mention Y."
Practicing is also vitally important for timing your talk. Your first attempt will ususally take longer than desired/required, but you should be running shorter than the target on follow-up attempts. If not, you need to cut down the content.
I gave a conference talk in May that was well under the time limit - I took barely 20 minutes in a 25 minute slot. It was a much smoother talk than one I gave in March where I tried to fit more material in. From now on, I'm going to err on the side of including less material, and giving myself more breathing room.
My daughter uses this type (Lessig-style?) of presentation in middle school. The class and teacher love it. Every other kid has about 30 minutes of unbearable, traditional Powerpoint slides filled with text that they read.
It's great practice for her. What surprises me is that even after seeing and appreciating this style of presentation several times the other kids persist with the old way.
If you're going to share the presentation, it's a decent idea to have a deck to present with and a deck to hand out later. If your presentation deck's a good read, that's what half your audience'll wind up doing instead of listening to you!
One trick a professor of mine used for slides was to blank out key words and phrases, so that the viewer sees a mystery and has to listen closely to the speech to find out the answer. Very effective trick.
As for presenting itself, that's all about practice. I usually paraphrase my written speech each time I practice so that I stay involved in the content, vs. just reading it.
This has always struck me as a combination of the worst of both worlds. By definition, if you're just omitting words in your slides that means you're coming close to reading them. And at the same time, you've made certain that your slides are useless after the fact.
In fact, that technique just strikes me as a lazy way for professors to force students to pay attention to presentations that are apparently not otherwise interesting enough.
A comprehensive slide will make the perceived value of the lecture and the slides equivalent. Hence you will skim over a slide and say, "oh, they're talking about this thing now" and then go comatose for the next few minutes. Leaving a single fact as an open question acts to raise the perceived value of everything else.
The slides aren't useless afterwards because the version put up afterwards may contain all the words.
Saying this is lazy is like saying that giving students problem sets without giving solutions simultaneously is lazy. It's the same principle - if you give out solutions, you are asking the students to not cheat by working backwards from the answer, to have 100% motivation to understand the problems on their own. No student is always that motivated all of the time in all of their coursework, but tricks like that will induce them to the extra effort.
Teaching has both "hard" techniques and "soft" ones. Using both will speed learning.
That's why your slides should be supporting your talk. The deck shouldn't be comprehensive -- your presentation of it should be. And if "the version put up afterwards may contain all the words"--if that's all that it takes to finish off the presentation--then, again, you're taking an annoying shortcut to try and get people's attention which will only serve to piss them off.
He's using Flash to embed different fonts into the document (SIFR), and the Flash plugin eats mouse events. Please, let real web fonts be widely supported soon...
I agree with what he says about slide design, but I think practicing your talk is the most important thing. I always give extemporaneous talks. Practicing doesn't provide you with a verbatim script, but it does provide you with certain ready-made phrases you can pull from your mind, along with the intuition of "I just said X, I need to make sure I mention Y."