From Chris Risdon, quoted in Laura Klein’s Build Better Products:
“Design principles must be based in research,” Chris explains. “You need to do some research where you have multiple inputs, such as quantitative metrics, stakeholder interviews, ethnography, or usability studies. You then converge on a set of insights–those are the things you’ve learned and that you wouldn’t have learned with only one input. Design principles are the output when you take those insights and make them actionable.”
For example, let’s say that you ran a usability test and got the insight that people weren’t reading all the necessary information before starting an onboarding process. You might turn that into a principle like “Learn while doing.”
“Learn while doing” may not seem like a more actionable insight than “take away the text on step one of the onboarding process,” but the thing that makes it useful is that it can be applied across the entire product. “Insights are tactical,” Chris says. “Principles are wider, but not so wide that you can’t judge design against them.”
When you adopt a principle like “learn while doing,” you give yourself a standard against which you can judge all future designs. When a new feature is built, you can ask yourself and your team whether it violates any of the principles you’ve adopted.
By making sure that all of the design principles are being followed, you give yourself a better chance of creating a consistent and cohesive user experience. Even if the product is being created by several teams working independently, you all have a single yardstick you can use to measure your design.