I happened to read following in a blog.

• The appearance of the device must provide the critical clues required for its proper operation – knowledge has to be both in the head and in the world.
• What makes design a highly challenging and rewarding discipline is that it grapples with the need  to accommodate apparently conflicting requirements. All great designs have an appropriate balance and harmony of aesthetic beauty, reliability and safety, usability, cost and functionality.
• Art and beauty play essential roles in our lives.  Technology changes rapidly, people change slowly.
• Humans do not always err, but they do when the things they use are badly conceived and designed.
• The psychology of everyday things demonstrate the importance of visibility, appropriate clues and feedback of one’s actions.
• Affordance refers to the perceived and actual properties of the thing, primarily those fundamental properties that determine just how the thing could possibly be used.  For instance, a round object is assumed to have an affordance of a ball.

  Something that happens right after an action appears to be caused by that action.

  Two fundamental principles of designing for people are : 1. provide a good conceptual model and 2. make things visible.

• Good designs have good mappings between the controls and the things controlled by them. For instance, the "next" button on a screen/wizard should be either on the right or bottom of the screen and not on the top left.
• Errors should be easy to detect, they should have minimal consequences, and, if possible, their effects should be reversible.  Errors can sometimes be prevented by using forcing functions.
• Designers can use three methods to prevent users get into an erroneous state:
  1. Intelocks – by forcing operations to occur in a particular order
  2. Lockin – by keeping an operation active, preventing someone from prematurely stopping it
  3. Lockout – by preventing someone from entering an erroneous state
• Ask the following seven design questions while designing – How easily can one:
  1. Determine the function of the device?
  2. Tell what actions are possible?
  3. Determine mapping from intention to physical movement?
  4. Perform the action?
  5. Tell if system is in desired state?
  6. Determine mapping from system state to interpretation?
  7. Tell what state the system is in?

real good insight for those stuck in design web!

Sounds cool…