Along with "don't pretend to be more technical than you are", I would add "Trust the engineer/dev/ux guy/programmer to do what you hired them to do".
I had the experience (that I imagine a lot of people share) of being hired by a non-technical founder in a start-up, who then wanted to micro-manage and give input on every minute decision that went into the building of the UI, even to the detrement of the user experience.