I've heard him say this in multiple interviews, so here it is for posterity. He shares these principles:
1. Seek out negative feedback. Ask your friends NOT to tell you what they like about your product, but rather what they don't like. Underweight positive feedback, and overweight the negative.
2. Reason from first principles rather than by analogy. It's easier to compare a situation or a problem to something similar to it and be satisfied by the analogy. It's much harder to actually think and reason about it logically as you would a physics problem.
The second principle is something that Larry Page said at the Google IO keynote earlier in the week too. He was making reference to the fact that from a purely physical perspective, the raw material cost of a smartphone is about $0.50 - $1.
This particular interview is actually quite old (not that it isn't still incredibly fascinating). The Foundation series has been going on for a long while, and Kevin has created 30 interviews with outstanding people.
If you have some time to spare, each interview is worth a watch: http://foundation.bz/
"I wasn't sure if that meant starting a company of if that meant working for a company that makes cool stuff," so I did both and started a company that makes cool stuff. Nbd, guys.
1. Seek out negative feedback. Ask your friends NOT to tell you what they like about your product, but rather what they don't like. Underweight positive feedback, and overweight the negative.
2. Reason from first principles rather than by analogy. It's easier to compare a situation or a problem to something similar to it and be satisfied by the analogy. It's much harder to actually think and reason about it logically as you would a physics problem.