A former drone operator, speaking on condition of anonymity, has revealed the methods used for drone targeting in an interview with The Intercept, the online publication Glenn Greenwald created as a vehicle to disseminate the information provided by whistleblower Edward Snowden. His story matches that of another former drone operator, Brandon Bryant, who has become an outspoken critic of the drone operations, and documents provided by Snowden.
There is no man-on-the-ground collecting information, establishing routines, or even making visual contact with the targets at all. Instead they rely on telephone metadata collected from the suspected terrorists' cell phones. Geolocation is part of that data, so complete daily routines can be established just by analyzing the data. That would be the same data the NSA was collecting on every American citizen, by the way. The same data they said was nothing to worry about because the content of your calls was still private. It turns out they can put together quite a bit of information about somebody with that data.
From the Intercept, "The former JSOC drone operator is adamant that the technology has been responsible for taking out terrorists and networks of people facilitating improvised explosive device attacks against U.S. forces in Afghanistan. But he also states that innocent people have 'absolutely' been killed as a result of the NSA's increasing reliance on the surveillance tactic.
"One problem, he explains, is that targets are increasingly aware of the NSA's reliance on geolocating, and have moved to thwart the tactic. Some have as many as 16 different SIM cards associated with their identity within the High Value Target system. Others, unaware that their mobile phone is being targeted, lend their phone, with the SIM card in it, to friends, children, spouses and family members."
We know of 4 Americans that have been killed in U.S. drone strikes, and only one of them was an official target. This is definitely the laziest way possible to locate and assassinate someone. Though, perhaps lazy isn't the best way to describe that apathetic, nonchalant attitude towards collateral damage.