Other interesting tips & phenomena from my small amount of experience:
- No one cares if you fuck up, seriously! A bit of self deprecating humor goes a long way here. "Ha-ha! I'm so terrible at this!" or even a more sincere "I'm terrified of public speaking so I forgot what I was going to say next!" usually elicits a laugh and sympathy. No one is natural at this, and most people don't practice it at all, and they don't want to. They get it.
- Following that, the only notes you should have are "checkpoints" as I like to call them. A 3 or 4 word phrase about what you're going to talk about in the next 30 seconds. If you forget, you fall back to the checkpoint, realize what you were talking about, keep going. An outline, if you will. Don't ever have "notes" that have exact wording in them. No! Disallow yourself to memorize wording, because that's how you lock up and forget. Instead, make sure you can explain each checkpoint yourself, to a friend. The wording will be different each time, and that's fine. You want that. It makes it more organic and gets you out of robot-recital-mode and puts you in ad-lib-i'm-good-at-this mode.
- While you're presenting, it feels like you're in warp speed. Things are happening so fast, and you're responding to them so fast. I suspect it's the adrenaline. Once in a while, you forget what you were going to say, or you think you're spending too much time thinking about an answer. Then you watch yourself on video and you realise it was only 2 seconds.
Even Michael Bay could have recovered from that by saying "wow, major brain fart!", and people would be commenting on how sincere he is. And if he hadn't memorized some impressive sounding bollocks word for word, and instead had a message to convey, he'd recover from that soon after.
If it's not just the presentation heebie-jeebies and you think you legitimately have crippling social / performance anxiety, you should try one of the many great programs out there that help you with that. In the Boston area, MGH has an entire center dedicated for that, I believe.
These basically help you develop those skills in a safe sandbox, until you get better and more confident, and let you go step by step.
There is no reason you can't try the same approach, if you think you can do it. Present at a small 10 person user group for your favorite obscure programming tool that you're passionate about. If there isn't one, start one! That way you can't avoid public speaking, and you know you're in good company.
Finally, re: Q&A: If you don't know the answer, say that you don't know! If you are thinking, think out loud so it's not boring and awkward for the audience. Both of these I see in tech presentations a lot.