Nothing drives home the fact of how much you don't know about your host culture than writing a book set there featuring characters who grew up there.
My current project takes place in England and is populated with native Brits. For the most part, people are people, and I've been here long enough to know how they talk and how they go about their daily business, so I shouldn't fall into obvious traps, like having a character talk about when she was in "high school" or making reference to a "senior prom." There are, however, numerous opportunities for gaffs.
After finishing the first draft, I reread it and took pages of notes highlighting details I needed to research. Such as: you can't go visit someone in the hospital (actually, the person would be "in hospital") here and expect the receptionist to give you a room number. Patients are on wards, there are nurses, but no candy stripers and some nurses, depending upon their duties, are called "Sister" or "Matron."
Registering a car, getting insurance, all different from my American experiences. They don't have appointment books, they have "Diaries" and they don't write things like, "Nathan said 'Hi' to me outside of math class today and I have a great big pimple in the middle of my forehead! I wanted to die!" in them.
What gets me is not the amount of research I have to do to make my prose not sound like it was written by an American (for one thing, in the above dialogue, I'd have to change Math to Maths and Pimple to Spot); I'm more concerned about the things I can't know:
What is it like to go through the British school system? What TV shows would they have watched, what pastimes would they have enjoyed, how would they and their friends have behaved?
But, to quote Donald Rumsfeld, those are things I know I don't know, and I expect a combination of creative prose and research will get me over those hurdles; it's the things I don't know I don't know that are more likely to trip me up. (By the by, that famously amusing "Things we know" quote makes perfect sense if you read it carefully.)
My biggest fear is that I will spend a lot of time on this manuscript only to send it off laced with unintentional hilarity like having a Memorial Day celebration and totally ignoring Whitsun, or having a character asking for a "round trip" ticket.
At least I know enough to not have a cop pull a gun.