Manager, Oakmark International
I caddied for a stockbroker 30 years ago, from age 12 to 16. He told me never to forget the cardinal rule of investing: Buy low and sell high. Today I rely on a spin-off of that rule: Buy good-quality businesses at low prices, even if it's counter to the crowd, and sell high, even if what you're selling is in vogue.
People these days are buying what's in vogue - energy and emerging markets - but this means those stocks are getting more expensive. Pharmaceuticals, consumer products and financials are the opposite, and the huge valuation differences provide an opportunity for long-term investors.
NEXT: It's hard to exploit a trend