1. Design principles:
   • Conceptual models
   • Feedback
   • Constraints
   • Affordances
2. All are important. This is what makes design such a challenge and rewarding descipline: it grapples with the need to accommodate apparently conflicting requirements.
3. Much of our everyday knowledge resides in the world, not in the head.
   The distinction between knowledge and information is not clear.
4. Design for failure.
5. The correct parts must be visible,and they must convey the correct messsage.

From Book "the design of everyday things"