User Centred Design Part 2: The Principles

1. Its empirical: Forget about big theories, this design method is about user behavior and user experience. 
2. It’s iterative: It’s a sociological process in which the research phase is followed by the phase design phase.
3. It’s participative: The user takes part in the design process, because of that the product needs to adapt to the user, not viceversa. 
4. It takes into account human diversity: Find the best fit / adjustment for the maximum number of people.
5. Taking into account that the user task, recognizing that the task is specific to each user. 
6. It has a systemic approach: the relationship between the user and the product takes place in a social, technical, economic, political and environmental.
7. It is pragmatic: it recognizes that there may be limits to what really is practical in each case and find the best result within those limits. 

This image from Pascal Raabe explain it: