We all understand that the ultimate slide is a visual composition that has such an emotional impact on us that the moment we walk out of the auditorium, we go and do something we did not plan on doing before.

For most day-to-day presentations, the objectives of a slide will be a bit more down to earth:

1. Can you actually read what is written on the slide from a distance (font sizes, graphs)?
2. Does it look as professional as the company/entity you are representing? Comic sans, clip art, low resolution pictures, distorted aspect ratios, PowerPoint bevels. (Professional and pretty are not the same things).
3. Does the chart just have one message?
4. Is information laid out so it supports the message? A trade requires pros and cons, a trend should come out of a graph, A implies B, there is a clear differentiation
5. Does the slide actually look pretty in terms of design, composition, balance?

Slightly related: here is a Dutch TV commercial from the 1970s with a quality inspector stamping "OK" on peanuts.