When you begin your presentation planning, start as basic as possible. Start with one phrase that sums up your core belief about your topic. Start with one question that could serve as the catalyst for your audience's thinking. Begin small and then grow from there - keeping only the important, timely, relevant and unique pieces of information.
This strategy will keep your information load low and drive most (if not all) of your content back to one central theme, point, lesson, etc. Both of these are necessary if you want your audience to retain and act upon your presentation.