Link: Ten Simple Rules for Better Figures

This Open Access article by Rougier et al. is an excellent tutorial in which they "provide a basic set of rules to improve figure design and to explain some of the common pitfalls."
 
Rule 1: Know Your Audience

Rule 2: Identify Your Message

Rule 3: Adapt the Figure to the Support Medium

Rule 4: Captions Are Not Optional

Rule 5: Do Not Trust the Defaults

Rule 6: Use Color Effectively

Rule 7: Do Not Mislead the Reader

Rule 8: Avoid “Chartjunk”

Rule 9: Message Trumps Beauty

Rule 10: Get the Right Tool