WASHINGTON — Globe-trotting humanitarian Greg Mortenson, co-author of the best-selling memoir "Three Cups of Tea: One Man's Mission to Promote Peace ... One School at a Time," keeps a reminder pasted to his bathroom mirror back home in Bozeman, Mont.: "When your heart speaks, take good notes."

Mortenson's own heart started hollering 15 years ago, when the exhausted mountaineer lost his way in northeastern Pakistan's untrammeled Karakoram Range. After stumbling nearly 60 miles down a glacier to the Muslim hamlet of Korphe — where he was welcomed as the first foreigner the 400 villagers had encountered — he watched local children substitute mud-coated sticks for pencils in an apricot orchard that served as their only classroom.

Inspired by his parents' work to start a hospital and school on the slopes of Mount Kilimanjaro, Tanzania, and by fellow climber Edmund Hillary's charitable work in the Nepalese Himalayas, Mortenson promised he would return to Korphe to build a school.

But unlike most well-meaning tourists touched by encounters with Third World poverty, Mortenson delivered on his pledge.

That unsuccessful shot at scaling Pakistan's K2, the world's second-highest mountain, changed Mortenson's life course from self-described "dirtbag climber" to literacy promoter, citizen diplomat and publishing sensation.

Since its publication in early 2006, "Three Cups of Tea" has sold more than 2.5 million copies in 29 languages. A young readers' edition with an afterword by Mortenson's 12-year-old daughter, Amira, arrives this month.

His nonprofit foundation, the Central Asia Institute (ikat.org), has built 78 schools serving 28,000 students in remote, politically volatile pockets of Pakistan and Afghanistan, and it runs nearly 50 others in regional refugee camps. Nearly all of its $2.8 million annual budget is funded by modest, individual donations — many of them inspired by Mortenson's story during one of his roughly 150 appearances a year at an eclectic mix of college and high school campuses, churches and civic groups.

The former Army medic, 51, who will receive Pakistan's highest civil award in March, has even been tapped by the U.S. military. He has lectured at the Air Force, Naval and U.S. Military academies, and he has shared his philosophy of curtailing Islamic extremism through education with such Pentagon brass as Gen. David Petraeus; Adm. Mike Mullen, chairman of the Joint Chiefs of Staff; and Adm. Eric Larson, SOCOM commander (Special Operations).

The soft-spoken, 6-foot-4 Mortenson hasn't strapped on a crampon since his fateful 1993 trip. (Along with writing hundreds of letters and collecting pennies from his mother's Wisconsin grade-school students, Mortenson's initial fundraising included selling his beloved climbing equipment and an aging Buick he had nicknamed "La Bamba"). But the onetime adventure tour leader says he still has an incurable wanderlust, and the travel lessons learned on his transformational journey are still with him.

When he launched the K2 expedition in honor of his younger sister Christa, a frequent travel companion until her death of an epileptic seizure on her 23rd birthday, "I was singular in my focus to reach the summit. It was linear and logical, and very Western," Mortenson says in Washington while juggling a family vacation with Pentagon and Capitol Hill briefings about his foundation's work.

"When I failed (less than 2,000 feet shy of the summit), it was humbling," he says. "But that failure opened my eyes to this incredibly beautiful area and the people who live there. If I'd reached my goal, none of it would have happened."

Too many adventure travelers, Mortenson says, "try to program too much. We become insular and encapsulated. ... We have our Gore-Tex and our satellite phones and our antibiotics, and we're always following an agenda.

"I'm not saying you need to travel the way I do," says Mortenson, whose exploits have included surviving an eight-day armed kidnapping by the Taliban in Pakistan's Northwest Frontier tribal areas and escaping a firefight with feuding Afghan warlords by hiding under putrid animal hides in a truck heading for a leather-tanning factory.

His hard-earned advice: Travel light (he spends about four or five months a year in rural Pakistan and Afghanistan with little more than a battered L.L. Bean carry-on). Don't be afraid to make mistakes and get out of your comfort zone. And carve out a few unscheduled days to interact with residents, such as sharing family stories and a cup of tea with mountain porters or stopping at a local school.

"When Gen. Petraeus read 'Three Cups of Tea,' " Mortenson says, "he sent me an e-mail with three bullet points of what he'd gleaned from the book: Build relationships, listen more, and have more humility and respect. And you can put that all into a travel context, too."