The two best ways to use them, from experience, seem to be:
- Super dense slides. These slides have a lot of text and are information-rich. You're not expected to read them, and the presenter will just skim over them, presenting a high-level view of each topic, but definitely not reading off of the slides. The slides are there as a rough guide to the talk, and as an in-depth resource afterwards. - Super spare slides. These slides have few-to-no bullet points, and are heavy on pictures. They're pretty much there to guide the speaker's narrative, and nothing else. At worst, there might be an inherently visual data element, like a graph.
The common element being that the slides are there to guide the talk, not be the talk. The reason powerpoints are so reviled is because people tend to just write a speech, put a bullet point in front of each sentence, and read it off a projected slide.