David Weber places a lot of emphasis on this too; I wrote down what I could remember of his discussion of the topic at ICON 2012:

Then Weber went onto a tangent I really appreciated: while working 4 assistantships at a university, he would tell his class that Hitler's actions were all highly rational & understandable if one understood his world view. An important writing rule: have no simplistic villains. The villains must have good reasons for everything they do.

Weber gave an example: the Mesan genetic slavers in his Honor novels. They are breeding a master race, and during the centuries, they have blighted the lives of billions - but they are all still human. So he described a scene from a book:

The leader and his wife are preparing for dinner in their rooms. The wife - "Oh honey, don't wear that red shirt." The husband: "but that's my favorite shirt!" Wife: "I know, and hopefully the geneticists can do something about your taste. And you're not wearing the red shirt."

(Everyone laughed).

A good writer makes bad guys comprehensible; hence, some fans come to opposite conclusions about Weber's politics, based sometimes, he said, on the same exact passages from his novels.

I think that part of this advice can be restated as "every character must think themselves the protagonist of their own lives" which I think I remember Orson Scott Card giving; though Eliezer's advice more explicitly focuses on how this affects their models of the universe.

A decade back, I was conciously attempting to use OSC's (if that's who I got it from) advice in a piece of Gargoyles fanfiction "Names and Forms" set in mythological-era Crete. In that story I had a character who saw everything through the prism of ethnic relations (Eteocretans vs Achaeans vs Lycians), and there's another who because of his partly-divine heritage couldn't help thinking about how gods and human and gargoyles interact with each other, and Daedalus in his cameo appearance treated everything as just puzzles to be solved, whether it's a case of murder or a case of how-to-build-a-folding-chair... (Note: It's not a piece of rationalist fanfiction, nor does it involve anything particularly relevant to LessWrong-related topics.)

It's also an awesome trick for interacting with real people who have an actual subjective world-view different from mine.

Unfortunately my mind can only effectively hold one human-size worldview at a time and so I am often confused by other people's actions or at best I second-guess my imagined cause of their behavior.

The other writer who also does this extremely well is Vikram Seth, in A Suitable Boy.