Most presentations are written by people without a professional graphics, design, or art background (including me). While it is almost impossible to catch up on the technical skills of these professional illustrators, it can pay off to take a daily dive in their work. The blog unstage (link here) is an example of a daily source of information that you should add to your RSS reader. Example below: a poster by Network Osaka. (I find poster designs especially useful as a source of ideas for slides.)
