Performance is random
Nassim Nicholas Taleb. Author, "The Black Swan: The Impact of the Highly Improbable"
Markets have princes but they never have kings. Nobody's thoughtful enough to make it for long without falling on his face; things change all the time. Most of the successes you see are just the product of luck; most market performance is random.
Stick with what you know
Richard Weiss. Managing director and senior portfolio manager, Wells Capital Management
If you know little about a company, shy away from it and stick with companies you really know about.