presentation tips ? (contd)

Adding to my previous post:
* I wonder if there should be at least one "hard" slide or concept in the presentation, which only a few will get.

One common suggestion about job talks is that the presenter should include some stuff that is a little in-depth to catch attention of the people who are closely following the related line of research -- mostly, to demonstrate the hardness of the problem and the significance of the presented result. I believe similar kind of expectations can be assumed for any other presentation as well. When people say "no equations", it does not mean "absolutely no equations" -- it is rather "no equations in most of the presentation, and a couple of key equations on that `hard' part of the presentation". In other words, there should be some motivation for the audience to look at additional details after the talk. They should not leave with a feeling that they understood everything. There are definitely some negative aspects of this approach, and I have a feeling that only a few people will approve of this. But, in my opinion, this has practical implications and avoids the risk of the talk being perceived as simplistic.