People are inextricable from their worlds.
Yes (no big surprise), characters in stories behave as if they are from the places that they're from. And when we hear or read them, we can tell. Automatically, subconsciously, the little hints add up.
So what does this mean?
It means a lot of things. One, which links back to my entry about point of view earlier, is that a writer should be careful to consider the observer's background experience in the world whenever writing descriptions. For me personally, this is the primary reason why I try to avoid third person omniscient point of view; I find it hard to decide whose point of view to use for the narration. Should I hop from head to head, like Frank Herbert did in Dune, or Mary Doria Russell did in The Sparrow? Should I try to imagine an independent storyteller telling the story, like C.S. Lewis did in the Narnia books? Should I stay mostly in one head but bring in regular glimpses of alternate points of view, like J.K. Rowling did in the Harry Potter series? Just thinking about that stuff makes me crazy! So my usual solution is to try to keep the narrative point of view as close to the character's point of view as possible, even when I'm using third person. The last thing I want is for my readers to be able to tell that part of the description was written from my own, the author's, point of view.
For me, close point of view is a fantastic way to keep a really gigantic and detailed world under control, because the limits on one person's perception and experience give you a great way to limit the kinds of information you're trying to dispense to the reader. It cuts down on the infodumping, big time. There are always things that characters don't understand about their own worlds - and that's okay. As long as your character knows what's going on, and lets people know when they're confused, that helps the reader figure things out.
Let me get down to some concrete details. My Varin world consists of eight cities, all of them built underground. They have good quality lighting to distinguish day and night, but it is provided by high-tech lamps all over the ceiling. So they don't talk about dawn, dusk, or twilight. They have dayrise and nightfall, and they have daylights instead of daylight. If somebody brings up a topic unexpectedly, they say that it "came out of the dark" instead of "came out of the blue." So vocabulary surrounding unique aspects of the setting should reflect that setting, as should expressions people use in conversation. So far so good.
The other thing I like to do with Varin is play with the fact that people who grow up in the Eight Cities aren't afraid of or bothered by being underground. It's totally normal to them - so of course when they go up to the surface, that's when things get weird. And by the way, they don't generally say "up to" the surface, but "up the surface" and "out the surface" - a dialect-like alteration to reflect their sense of place. I'm sure none of you are surprised that the idea that Varin citizens would find the lack of a roof scary, or outside daylight very bright. But as I've spent time developing my world and the characters in it, I've tried to push it further than that. When we describe things, we often say what they're like, and we generally compare them to things we know. So I'll have a character compare a waving field of grass to billowing bedsheets, or a rock face gleaming with sunshine to a clean plate. A sort of reversal, where daylight could be "as bright as fire" but not vice-versa.
The huge temptation for me, and I'm sure for many others who really love the worlds they've created, is to try to give too much, or to fall into infodumping. This to me means taking attention away from the story - the central drive of the narrative - and putting it instead into lots of explanatory details that are intended to flesh out how the world works. The single principle I've found most helpful for controlling my tendency to go crazy infodumping is that of relevance to point of view.
People do not talk or think about things that they don't notice, things that aren't important to them, or things that are so normal that they don't stand out.
Take for example an alien. That alien thinks that everything about his world is totally normal, and so he will generally not explain it. He has no reason to! But change the context - put that alien in a conversation with a human being - and suddenly everything changes. The presence of contrast will cause the alien to notice things about his own world, people, language etc. - but still, those things he notices will depend on surrounding circumstances. The alien's state of mind (calm and reflective? anxious and aggressive? in a state of shock?) will affect the kinds of things that he notices.
And don't forget to ask yourself: would this alien really refer to his people as "the Gegogians"? Or would they be "my people"? Under what circumstances?
I'd like to add one final note on using invented words for elements of a world. Invented words are wonderful fun, and they demonstrate the language of a region. Wonderful. They also make for a sense of alienness, of not being in the world we're used to. But to be used most effectively, they need to have a lot of supportive surrounding context. I don't remember who it was that said "if your world has rabbits, then call them rabbits," but they had a really good point. When too many things have foreign names, the reader can be distracted, and start to dissociate from the setting instead of staying absorbed in it. In Varin stories, a sense of familiarity is more important to me than a sense of alienness, so I tend to use names like "kelo mushroom" or "river lettuce," or even just "apples." In my linguistics universe I want to go a bit more alien, so I'll talk about "white-spotted gharralli furs," (who knows how big a gharralli is?) or "grazers" (it might eat like a cow, but I'm betting it doesn't look like one!).
I feel like I've barely scratched the surface of this topic, so I'd really love to have some questions or comments, so I can return to it in the coming days.
A final thanks goes out to my awesome friend Janice Hardy, who put me onto the word "daylights" just a few weeks ago (after I've been working with Varin for more than ten years!). I'll shout out for her a little, too - she's got a great fantasy novel she just sold, called The Pain Merchants, and yes, it is as amazing as it sounds. Watch for it!