[scheff]

As a long time programmer, I've learnt the mantra "somebody has already solved this, let's go find their solution." That applies to pretty much any technical or non-technical issue that you need to solve. So much of what we need to know is written up somewhere on the internet, leaving us to focus on the 1% of the problem that we alone can solve, and differentiates our value proposition from all the other alternatives.

My short answer would be "know enough to be dangerous, and surround yourself with smarter people".

Recommended reading - http://www.sacred-texts.com/nth/tgr/tgr10.htm

Start from 'Henry Ford was called "an ignorant pacifist."'