The document discusses 5 common mistakes to avoid when designing PowerPoint presentations: 1) including too much text-heavy content on slides, 2) not using enough visuals, 3) using low-quality or pixelated images, 4) having an inconsistent or scattered design with fonts, colors and alignments, and 5) lack of preparation and rehearsal for the presentation. It encourages the reader to spend time designing beautiful, visually engaging slides with a cohesive theme rather than just slapping content together last minute. Proper preparation including gathering content, designing slides, and rehearsing is emphasized as critical to giving an outstanding presentation.