Like most trends, at the beginning it's driven by fundamentals, at some point speculation takes over. What the wise man does in the beginning, the fool does in the end.

Chains of habit are too light to be felt until they are too heavy to be broken.

The three most important words in investing...Margin of Safety.

Focus on return on equity, not earnings per share.

... but the important thing is that when you do find one where you really do know what you are doing, you must buy in quantity.... Charlie and I have made a dozen or so very big decisions relative to net worth, although not as big as they should have been. And in each of those, we've known that we were almost certain to be right going in.

To be successful, you should concentrate on the world of companies, not arcane accounting mathematics.

Yeah, we don't consider many stupid things. I mean, we get rid of 'em fast...Just getting rid of the nonsense -- just figuring out that if people call you and say, 'I've got this great, wonderful idea', you don't spend 10 minutes once you know in the first sentence that it isn't a great, wonderful idea...Don't be polite and go through the whole process.