I recently answered a Quora question on what is the best way to get started with a VC/investor presentation. The answer applies to all presentations, not just investor presentations. Obviously, this is my preferred approach, yours might be different.
I use multiple approaches at the same time, in parallel:

  • Scribble a story line on paper, or an iPad mind mapping app (iThoughtsHD is good)
  • (Just because I like it) design a really beautiful cover page with a nice image and the right look and feel of the deck.
  • Dive straight in and try to craft that ultimate killer slide, the one that makes the most important point in your presentation and finish it all the way. BANG.

Then I continue to iterate: refining the story line, adding a chart here and there. I take lots of breaks in the entire process, designing a good deck can take a lapse time of about 2 weeks. This ensures that your creative energy stays fresh. Presentations made at gun point at 3AM before the 9AM meeting never look really good.