When it comes to public speaking, “less is more.” The simpler a presentation is, the clearer and more memorable it will be — and the more time needed to prepare it. Unfortunately, this principle is apparently underappreciated. According to a survey quoted in the book “Resonate” by Nancy Duarte, 86 percent of executives say communicating with clarity directly affects their career and income, but only 25 percent of executives devote more than two hours to preparing for high-stakes presentations. Tips for crafting simple, clear, memorable PowerPoint slides: Solicit advice on your presentation from people who have addressed your target audience.…