‘Prototype’ and ‘Know your people’ as the two imperatives for all designers.
“In our research of what separates the great designers from good designers, we saw that the great designers spent a lot more time trying to understand the problem. They really dove in deep, focusing on all the aspects of how their design would be used and what the constraints and complications might be. Design is all about tradeoffs. Learning how each tradeoff affects the outcome is core to great design. One of the things we saw from the best designers is their use of prototypes to explore the problem. The prototype is the instrument they used to uncover previously hidden constraints and to see the shifts in the outcome of the design.”