Principle
The main thing; the motivation
My work is guided by a collection of philosophic principles on both strategic and tactical levels.
The most pervasive design principle for me is simply form follows function. This requires an identification of function, naturally, and function can pursue a wide variety of goals. I am most effective designing for goals and functions that are fairly concrete and measurable, such as ensuring that information is presented in unambiguous and accessible ways. One consequence of this is that I enjoy mapmaking in all its forms, whether the territory is geographic or conceptual.
Design that elevates form over function can easily be poor design, however competently or beautifully executed it may be. An small technical example of this is presenting contact information on a website in such way that a visitor can't copy and paste it into their address book. I very much value good typography and all, but forcing people to retype such info, risking typos as well as inconveniencing and possibly annoying potential customers and stakeholders, suggests to me that the responsible designer got caught up in preserving cosmetic goals and lost sight of the real point of providing such information (and even the point of the website itself).
A couple of guiding inspirations
Robert Bringhurst (The Elements of Typographic Style) is my main man in the field of typography. I aspire to his elegant approach and function-driven philosophy, such as avoiding habits we've come to think of as normal or proper but that exist only because of arbitary limitations of current and past technologies, or just because the reasons for certain practices aren't properly understood. A simple example is the oft-seen indenting of the first line of initial paragraphs. A paragraph first-line indent exists to identify the beginning of a paragraph. In the case of an initial paragraph, this issue is moot. Related to this is the use of both an ident and additional leading between paragraphs. Use one or the other — to use both is redundant.
Edward Tufte is my primary inspiration and reference in the area of information graphics. Like Bringhurst, he challenges us to not let our design decisions be driven by our software tools. He condemns what he calls "chart-junk;" embellishments such as three-dimensional effects for bar charts that add nothing to the data set and can actually obscure the data. Applying his criteria to the visual presentation of information results in graphics that may not thrill editors at USA Today, but they will offer clarity, integrity, and timelessness.