In 1970s Dieter Rams (a German industrial designer) questioned himself with one but very important question: ‘Is my design good design?’. Result, the ten most important principles for what he considered was good design.
1. Good design is innovative 2. Good design makes a product useful 3. Good design is aesthetic 4. Good design makes a product understandable 5. Good design is unobtrusive 6. Good design is honest 7. Good design is long-lasting 8. Good design is thorough down to the last detail 9. Good design is environmentally-friendly 10. Good design is as little design as possible