8. Don't show the number of the slide
[field20]
It may seem like a nice gesture, but the feeling it evokes in the audience is more ‘how many slides I have still to powerthrough’ or ‘Jeez, slide 23 out of 80, and we’re already nearing the end of the time slot!’ than ‘would you look at that, we’re at slide 23 out of 80’. It has a noble thought behind it, but why not just keep their attention with a good story? In addition, there is the issue of spare slides that you may use for questions, that inflate the number of slides and discourage your audience even more.