The following constitute version 1 of my personal principles of design:
1. Design objects and use materials that become more beautiful with age. When scratches, dirt, and exposure to sunlight lend an object more aesthetic depth and loveability, then one ceases fighting a losing battle against inexorable entropy and can embrace the nuanced aesthetic of age. Synthetic materials, generally speaking, need not apply.
2. Keep required maintenance to an absolute minimum. It is natural and healthy to maintain objects, but poor design translates into disproportionate amounts of time being spent keeping objects usable rather than actually using them.
3. Design in such way that the object holds the potential to adapt to unforeseen future functions. Evolvability insures the object against the yawning, ubiquitous dumpster. It integrates into new and developing circumstances that the user and/or the object may find it/him/herself in.
4. Provide a concrete and elegant framework that conduces to user-customization. Design is valuable insofar as it delineates specific forms and ordered systems from a near infinity of potentialities, but can also be detrimental insofar as it restricts potentialities from emerging naturally. The trick is to strike a balance between elegance of an organizational/structural framework, and the fluidity of possible applications.
This list of principles is by no means done; the above points merely represent my current conscious assumptions from which I am designing and producing.