The way I work: I pick a country. I learn the political history - I mean I really learn it; I read until it sinks in. Once I read the political history, I can project and find the clandestine history. And then I people it with the characters.
I just became what I call an 'anti-fascist novelist.' There is no word that covers both the fascists and the Communists, which mean different things to people, but of course they're the same: they're tyranny states.