A great place to learn about and create Design Principles.
Here are some books worth exploring:
A Pattern Language, by Christopher Alexander et al is one of the most important books even if you have just a passing interest in any aspect of design! The book is broken into small sections called “patterns,” each of which details an observation about the way that people relate to space, and how space can shape human life and interactions for the better. The patterns begin at the large scale, with cities and downs, moving down through neighborhoods and streets, and then into houses, yards, rooms, and furnishings.
The book is a doorstop, but you don’t need to read it cover-to-cover to benefit. Skim the contents to find patterns that catch your eye. These will help you better understand your home (and neighborhood, city, or town) and the way you live in it.
100 Things Every Designer Needs to Know About People
The Non-Designer’s Design Book
Designing with the Mind in Mind: Simple Guide to Understanding User Interface Design Guidelines
On Universal Design
Universal Design, which means creating products, services, and spaces that are accessible to all people, regardless of age, disability, or other factors. It’s applicable to so many mediums, from pedagogy to game design, all the way to civil engineering and medicine. Understanding the 7 Principles of Universal Design will not only enhance your career, but elevate your understanding of how the world works.