Katherine Boo, who has a recent book on the slums of India, describes her process. She finds that "listening and observing often work much better [and] reveal much more about the complexity of someone than the answers that they give to questions about themselves":
Often the people who have the most verbal dexterity have had some amount of education in their lives, and you don’t want to limit your reporting to just those people. You take a kid like Sunil, the young scavenger, he’s been raising himself, so conducting long interviews and eliciting illustrative anecdotes was out of the question. When I started spending time with him, it became clear that Sunil had an extremely strong aesthetic sense that helped him through life. Moments of natural beauty were very important to him. For example, there were parrots on the other side of the sewage way, and some boys would climb up and capture the parrots and sell them at the market. Sunil felt so strongly that this was wrong. He thought the parrots should be left where they were so that everybody could hear and see them.
Another time, he found six purple lotuses blooming on an airport wall and protected them, kept them a secret, so that no one could cut them down and sell them. These aspects of his character emerged over time from observation. I wasn’t going to get them through conversation. It’s one thing to have somebody talk about what they value in whatever language they have; it’s another thing to really see what they value. And with Sunil, after it became clear he had this sense, I could talk to him about it. I still asked questions, and a lot of them—endless questions if you ask some—but what works best for me is when I can observe something and then ask the person about that moment afterward.
The Dish 