Those who become hyperpolyglots are those who meet two criteria. One, they are exposed to language material. Two, they undertake learning languages as a mission as well as acquiring the personal identity as a language learner. I describe the "neural tribe theory" of hyperpolyglots, arguing that they possess an atypical neurology that is selected by some environments and not others; presumably, there have always been humans walking around with that set of neurological traits or factors, only some of whom actually use those things for languages.
I always get role models, people from real life who've lived the lives of the characters, and talk it through together, me, them and the actor, a lot. That helps. We certainly have our disagreements. But in the end we trust each other.