Since this is for writing novels, I'll tell how I've done mine. First, I get interested in a subject. I go to the library and get a few books or periodicals on the subject. Then, while reading the books I jot down things that I think would be useful to look up for my novel. Pretend I am writing a novel about a novel about a prison riot in the 1930's. I'd first look up things on crime, the prison system, not only from the view point of the establishment, but also from the viewpoint of the prisoners. What sort of punishment was there for bad behavior and so on? Since good dialog means that you speak oblquely, I need to find other things for the guys to talk about-- baseball is good. The Bible, the law, their families, as we as concerns about guards, trustees, and other things (yeah, I saw the Shawshank Redemption too). Whenever a good article comes up try to see what they refer you to in that. You'd have lots of things to the location, the clothes, the cars, what was important to them. But I still would start at a brick-and mortar library.
I think writers (especially freelance article writers) are compulsive clipping collectors. Any interesting thing will get the response of putting it in a file folder to save it.