The Washington Post has an article by Bob Woodward telling how a phone call to a courier led the US to find Osama bin Laden.
Woodward writes: "It seemed an innocuous, catch-up phone call. Last year Abu Ahmed al-Kuwaiti, the pseudonym for a Pakistani known to U.S. intelligence as the main courier for Osama bin Laden, took a call from an old friend.'Where have you been? inquired the friend. We’ve missed you. What’s going on in your life? And what are you doing now?'
"Kuwaiti’s response was vague but heavy with portent: 'I’m back with the people I was with before.' There was a pause, as if the friend knew that Kuwaiti’s words meant he had returned to bin Laden’s inner circle, and was perhaps at the side of the al-Qaeda leader himself.The friend replied, 'May God facilitate'.”
Woodward says: "When U.S. intelligence officials learned of this exchange, they knew they had reached a key moment in their decade-long search for al-Qaeda’s founder. The call led them to the unusual, high-walled compound in Abbottabad, a city 35 miles north of Pakistan’s capital."