This is how I go about creating a presentation. I've listed out the phases of prepration as well as the approximate timing of each phase (in relation to the length of the presentation).
First, I make an outline of what I want to share. This outline includes a description of the audience, what I want them to take away from the presentation, and and abstract of the content. It also includes a detailed list of bullet points describing the flow of the presentation.
The purpose of this outline is to organize my thoughts at a high level in a way that is relatively cheap to iterate on. I want to have the main flow solid to avoid expensive rework on a more finished version.
Time: 2x
I translate the outline to a slide deck and get quick, Ignite!-style visuals for each slide.
Time: 3x
I try to give the presentation based on the slides. The purpose is to see where the flow of ideas is unnatural or needs to be augmented. I also can see how the slide images or content need update. I incorporate feedback and ideas in realtime as I am talking. Eventually I get through it once.
Time: 3x
I do a rehearsal of the presentation. It's still pretty rough.
Time: x
I view the rough rehearsal. I incorporate any feedback. I rehearse again.
Time: 5x
I view the polished rehearsal. I incorporate any feedback. I rehearse one last time. This rehearsal is usually done close to the time of giving the actual presentation.
The purpose is to have a solid, sparkling run that incorporates all of the feedback and gives confidence to the actual upcoming presentation.
Time: 3x