Here is the summary of common wrong practices in delivering presentations pointed out in this wonderful talk:
More than one message per slide. People will randomly ignore one.
Read sentences on a slide. People cannot read and listen at the same time.
Important objects are in small sizes and low contrast. People will pay more attention to your slide title because it is bigger.
Black texts on white background for slides. It gets high contrast and steals people’s attention away from the presenter.
More than six objects per slide. It takes too much energy for people to figure out which is which.
Set limit on number of slides instead of objects per slide. A 4-slide presentation with crowded slides may take longer time to finish and is harder to understand than a 40-slide one with each slide dedicated to one message showing less than six objects without long sentences.
I cannot agree more. I have heard the following suggestions from professors to their students:
“Don’t prepare more than 10 slides if you give a 10-minute talk otherwise you won’t be able to finish it on time.” However, I’ve seen people talked for more than half an hour in front of a single slide. You have to rely on rehearsals to get the time under control. PowerPoint and similar tools allow you to record the mount of time you spend on each slide.
“Write down what you want to say on slides so that you can read it during the presentation.” You will become the most boring presenter if you turn your back to your audience and read your slides.
I have only one concern regarding point 4. For technical topics, images on slides are normally more important than the face of the presenter. A professional figure on a white background is perfect to attract people’s attention.