Once I've done #talktips 1-5 (Who I'm talking to, What I'm talking about, How long I should be talking) I begin breaking all my thoughts and notes into an outline. Since, to date, most of my talks have had accompanying slides, I create my outline in a Keynote deck (I used to use Illustrator artboards to make my slides, switched to Keynote about a year ago.) It's extra handy if the conference organizers have provided projector/screen specifications so I can start at the correct size. When in doubt I go with good ol' 4:3 aspect ratio.

My slides almost always contain only one word. From there I use the "notes" area to write out the meat of my thoughts around that one-word prompt. If I absolutely must have more than one word on a slide, I'll do it, but I mostly try to avoid more words.

I only started doing this approach a year or so ago, which was part of my reason for switching to Keynote over Illustrator. It allows me to move things around a lot more easily.

Bonus:
While I've put some thought at this point into the aesthetic of the slide (minimally, background color and font choice), I don't spend much time on the visual aspects until I've got a pretty tightly flowing talk happening. I've spent far too many hours working on making/searching for art for slides that end up dropped, now I save this part for later.

Note: All tips written for my #talktips #30days challenge are written in 5 minutes or less.
if you have more questions or would like more info about any of my #tinytips, leave a comment!