Type design may be intimidating to many, with terms such as leading, baseline, kerning, ascender, tail, and many more … The good news is, there are eight basic, universal typographical design elements: typeface, hierarchy, contrast, consistency, alignment, white space, and color. Even a basic understanding of each of these elements can revolutionize any design project.
Typography
Typography Elements Everyone Needs to Understand — Gravit Designer Blog
Knowledge
Steal Like an Artist: 10 Things Nobody Told You About Being Creative
An inspiring guide to creativity in the digital age, Steal Like an Artist presents ten transformative principles that will help readers discover their artistic side and build a more creative life.
Craft
Steal Like an Artist: 10 Things Nobody Told You About Being Creative
Anyone including non-designers can use this framework to analyse a product or service or analyse a piece of work for a potential client. You could even use this to review your own work as the tools and techniques I use leave little room for bias.
Jakob Nielsen's 10 general principles for interaction design. They are called "heuristics" because they are broad rules of thumb and not specific usability guidelines.