Audience perspective

The PowerPoint or Keynote slide sorter view with the small thumb nails is a good proxy for how the audience will see your slides. But sometimes, they are even worse off as in this image by Ali Eslami.

While I would not go as far as recommending to fill the top of the slide with all the important content, it is true that this is the part of the slide that will get the most visibility. At least write the message clearly in the headline, rather than using the space for a descriptive title.