Design is vague. I know. In this context, I’m referring to both system design and graphic design.
When I design anything, my top priorities are usability, accessibility, and beauty. With these principles in mind, I built a17t, my CSS library, and designed several other websites (including the one you’re on right now). I also do my best to apply these principles to software design and writing, but that’s harder to showcase.
P.S.: In my (limited) experience, the principles I mentioned above almost always work together. A design with great usability will probably be accessible and beautiful, and vice versa. (That’s not to say that special effort isn’t sometimes required in some categories, especially accessibility.) As a bonus, I’ve found that the best design is often the simplest — so I try to avoid complexity wherever I can.