How to build great leaders

20 November 2009:

For John Tolva, IBM's Chicago-based director of citizenship and technology, the value of his four-week assignment to Ghana last year really hit him during a game of Scrabble by candlelight.

He and teammates from India, Germany, Brazil, and other countries had agreed on an unorthodox rule: You could use any language you knew. "That's when I understood what a globally integrated enterprise looks like," he says.

He and the others were forced to ask "what connects us," since it obviously wasn't language or culture. The real connection, Tolva says, is "the values that IBM has instilled in us. It's a professional code that isn't written down -- but it's there."

The group of 10 was part of IBM's two-year-old Corporate Service Corps (CSC), which sends teams around the world to work with local organizations on local problems.

Tolva's group was helping create a program for promoting Ghanaian handicrafts globally. The job "stretched me in a way we all absolutely need," says Tolva, 37, who has since been promoted to his current executive-level job. "It gave us a shake in perspective." It also means that "there are now nine other people in the company I would trust with my life."

Developmental assignments like his are among the most important tools that great companies use to build leaders -- and that average companies rarely use at all.

The importance of such assignments and how they're being adapted to pay off in today's global economy are two of the strongest messages emerging from the research behind our new ranking of the world's Top Companies for Leaders.

Fortune has joined the human resources consulting firm Hewitt Associates and the HR services firm RBL Group to identify companies around the world that are best at attracting, developing, and keeping business leaders.