Rule: Know you don't know everything and being willing to learn what you don't know.  

"I was not in fashion or retail before I opened WHARF. I have built brands before as a marketer, but never anything like trying to start a brand (and store) from scratch. I had my business acumen, an idea, and the motivation to see it through. But along the way I have invested countless hours researching, talking to experts, visiting factories, other brands, other stores, etc. All of the knowledge I did not possess about the business is out there, so if you are willing to accept there are people smarter than you, with more expertise in what you are trying to achieve, be humble and ask them."