We started with an outline: a set assumptions about who the audience was, what they needed, and the message we wanted them to hear.
After assigning roles for the multi-person talk, it came time to build one slide deck to visually communicate the message and integrate the speakers into a unified whole.
My first draft translated the outline into potential visuals:
I edited out several slides after reviewing this rough draft: a few were unnecessary, a few didn't work, and a few were too tough for my brain to draw.
Next I moved from potential visuals to slides that could actually work. For this stage, I used a massive piece of paper and with a pen traced little boxes that have the same aspect ratio as the slides. Then I drafted the slides themselves.
After working for about 45 minutes, I booted up the trusty old Keynote and away we went.
Key success factor: Keynote is the last part of my workflow. Know what you want to make before getting into the detailed canvasses, options, and menus of the slide-making software.