We believe that almost all really good investment records will involve relatively little diversification. The basic idea that it was hard to find good investments and that you wanted to be in good investments, and therefore, you'd just find a few of them that you knew a lot about and concentrate on those seemed to me such an obviously good idea. And indeed, it's proven to be an obviously good idea. Yet 98% of the investing world doesn't follow it. That's been good for us.

If you have competence, you pretty much know its boundaries already. To ask the question (of whether you are past the boundary) is to answer it.

In Gillette's case, they keep surfing along new technology which is fairly simple by the standards of microchips. But it's hard for competitors to do. So they've been able to stay constantly near the edge of improvements in shaving.

Anyone with an engineering frame of mind will look at [accounting standards] and want to throw up.

Determine value apart from price; progress apart from activity; wealth apart from size.

Once you get into debt, it’s hell to get out. Don’t let credit card debt carry over. You can’t get ahead paying eighteen percent.

Understanding both the power of compound interest and the difficulty of getting it is the heart and soul of understanding a lot of things.