AMK's talk How to Give a Python Talk is very informative, you should watch it even if you aren't planning on giving a talk. Why should you watch it? partly because it gives you an idea of what goes into a talk and partly because it demystifies giving a talk enough that it might prompt you into giving one. Lots of solid advice.
Andrew's talk itself is a nice illustration of some of his points. No one would mistake Andrew for a motivation speaker; you don't walk away from that talk with an inexplicable need to buy what he's selling and given the audience you might actually be pissed off if you thought he was trying to sell something. (talk->content != NULL) ? Good_talk : Bad_talk. PyCon attendees care more about red meat than glitter and are very forgiving on presentation if the red meat is there.
How I do it what I do to prepare has heavy overlap with what Andrew recommends. Practice is king. When I step on the stage I'm not nervous per se, but when speaking in front of a large audience I do tend to read the slides much more than I talk about them in practice. So my rule of thumb is to practice a talk where I spend three minutes per slide knowing that I'll drop most of my segues and only spend one minute live talking per slide. Figure out your own constant and practice against that. I was amazed at Ned Batchelder's talk because the the video of his talk matched so closely with his text explication of his slides. The prepared text is almost 1-to-1 which I personally just can't do.
Narrative, Narrative, Narrative: Pick a theme and stick with it. If you don't talk to your premise once every couple minutes then you have failed. My talk was "Class Decorators: Radically Simple" and I tried to say on every example that a decorator was a callable that took one argument and returned something. Raymond Hettinger's talk was "Easy AI in Python" and he started and finished every example emphasizing that a novice could do it. Alex Martelli's talk was "Abstractions as Leverage" and he introduced every slide with a quote from a very dead (and sometimes white) male who had made the same point back when writing was a novelty. It seems odd but part of your job as a speaker is to repeat yourself, repeatedly.
Don't drink coffee: This sucks, but you can't drink your normal amount of coffee before your talk. I was hoping to drink a few cups and balance it out with a bloody mary but my talk was in the AM and the hotel bar wasn't open. Instead I drank only a little coffee so I wouldn't be humming on stage. I'm told Beta Blockers work to suppress the nerves (symphony orchestras use them) but I haven't tried it myself.
Practice is free and Plentiful: It is a not-so-secret fact that user groups, PIGs, and even Cons are starved for presenters. My most recent talk started as a lightning talk and then I gave it at a local user's group and a couple Cons that had 90%+ acceptance rates before giving it at PyCon. Practice is good and the opportunities for practice are many.
You already know something to talk about At the Boston PIG talk-dry-run (all the PyCon presenters gave their talk to 30 people a week before they gave it to 300+) I spent the first five minutes talking about talking. You do know something you can do a talk about and it sounds like "what is something I wish I knew about one year ago?" It's that easy. Try one or three ideas on the local group as a lightning talk and then grow the best one into a proper talk proposal.
It isn't complicated, see you with a speaker's badge next year!