Crap I'm speaking at [insert conference here]. How do I prepare?

I'm actually the opposite: I tend to avoid being paid to speak (one time I was actually paid, but I didn't cash the check), but if you want to record a video of me speaking for your usage on your website, then I consider that something you really need to be saying up front and which you should probably be paying for (and thereby which I often just won't do, as I usually avoid being paid; my standpoint on avoiding being paid will probably change over time, though).

The first issue is that it isn't really "publicity" for me (to respond to your linked point #3 about wanting publicity), it is free and valuable content for the event: to the extent to which I obtain publicity, I get it from the people at the event that I am addressing with my talk, not from the people who run the event; the second one is that recording the video to go with the slides doesn't mean that the content will now be understandable, as I feel truly awesome content is often somewhat interactive (I try to break the ice quickly to allow questions to interrupt me); and, finally, it has a severe cost on the talk... when you are speaking with a smaller circle, you can tailor your talk to directly meet their needs (I make it a point to meet as many people as I can before I give a talk to ask why they are attending the conference, what they wanted to get out of it, what company the work for, etc. and I then retarget my talk to directly serve those interests, use language appropriate to the audience, and sometimes can come up with specific and more useful examples), but when you know that thousands of random people are going to be watching this recorded later you suddenly have to talk to a general audience and have to be more guarded about stories and predictions (as you will certainly be called on them years later in drastically different contexts)... it really just ruins the experience.

(edit:) In essence, it is actually a different medium from a "live" talk: a talk that is being recorded is to a different audience (undermining the goal of having a conference tailored to specific topics and interests) and has different constraints (difficult interactivity with either the audience or the slides, a tradeoff on movement on stage vs. framing of the camera), in the same way that a slidedeck without an associated talk is a different medium from a talk; you aren't really giving a talk to a conference anymore: you are giving an address to the world.

I find that I don't need to write down nice turns of phrase - if they're really nice, I naturally remember them, and can't help but hit them when I get to the subject.

I always start in my head with the goal of the speech, then I sit down and make a quick outline.

I use the outline as a skeletal structure for my slide deck, otherwise I spend hours tweaking font size on the slides instead of understanding the overall goal of the talk. Once the outline is done, I add in a bit of muscle to the talk - one to two sentences per point to the outline. Then I go to the slides and add full-pages images for each slide, with short topic headlines for each part of the talk. Then I memorize the gist of the outline sentences and embed those mentally into the slides (making the slide deck a memory palace). When I get up on stage, the slides remind me of the storyline or topic I'm on, and I simply tell the story.

I have written out some talks before, but I only use that method to practice the talk as if I were speaking it out loud. I write with the same tone of voice that I speak in, and write it to get it out of my system. I don't look back to the write-up afterwards.

Neil Patel recently wrote some helpful advice for public speaking, even if you hate it

http://www.quicksprout.com/2012/12/03/how-to-speak-in-public...

I've found that the weakest part of many presentations is in the transition from one point or idea to the next.

Shaky transitions are a prime cause of audience disinterest, and poor flow can quickly remove the auditor from the energy and flow the speaker has established, which makes such a time perfect for checking twitter and FB and otherwise disengaging.

The boundaries between ideas should feel natural and smooth, and I think for many it's difficult to arrive at a natural transition without getting very intentional about it, i.e. writing it out.

So I say write it down, edit, speak chunks out loud, and edit more.

In this way, the presenter can craft the most important sections with style while becoming familiar enough with the material that the delivery feels quite natural.