In addition to the slides below, I would like you to take a look at a couple of great resources that further illustrate the concept of visual hierarchy:
Specifically, see these two examples of taking plain text and creating different visual hierarchies with it:
This is an article about visual hierarchy that I used to prepare the presentation for class, it’s a very good read.
I also came across this other presentation on visual hierarchy for Web design which you may find useful, from the author of the book Site Seeing: A Visual Approach to Web Usability.
And here are the slides I used in class: