A big part of SF and Fantasy writing is the world-building – creating the illusion of an entire culture out there that exists independently of the story you’re telling. If the illusion is well done, the piece feels more solid and will often be much stronger even though the world-building doesn’t directly impact the characters or plot (it does, and should, impact them indirectly by informing their choices and their view of how their world works – Athena Hera Sinistra’s shock and confusion dealing with Eden in Sarah’s DarkShip Thieves is a good example of how this works).
So how do you do it?
The reality is that many authors “cheat”. Just as plots are borrowed wholesale from history and have the serial numbers filed off, so too are settings. The best borrowings enrich the story soil by working with the plot and characters to make the whole piece stronger. Pratchett’s Discworld books are probably the best example of this: Ankh-Morkpork is sufficiently developed that the city is damn near a character in its own right, complete with interesting history, landmarks, and of course the river Ankh. The broad base of a medieval European city is there, with the Discworld version of early Victorian industry, and such a collection of bits and pieces from different places and times that the effect is much like a place that has grown and evolved from its earliest settlement.
Just how much Pratchett has borrowed from different parts of history (and any other field of knowledge he can get hold of) is astonishing. I’ve yet to encounter an obscure bit of historical trivia that wasn’t at minimum a throwaway line in a Discworld book – but I doubt Pratchett is going consciously “Oh, I’ll do a piss take on the Peelers next.” No, what he’s doing is absorbing an eclectic mix of odd facts (he said at the last North American Discworld Convention that he collects books of obscure Victoriana and history) and they take a twist in his brain before emerging into something that looks and feels fresh – but if you look you can see the original source there. The clacks in Going Postal did exist. They were used in France about 50 years before the telegraph got started – but not quite the way Pratchett revisioned them for the Discworld.
There’s also explicit borrowings. I won’t spoiler anything, but Sarah’s A Few Good Men has very strong echoes (deliberately) of the American Revolution. There are hints there of pre-revolutionary France as well – also deliberate, and Sarah has said that Liberte Sea City will have a French-style revolution which will end about as well as the real one did (badly). Those who know their history will find A Few Good Men and its direct sequels have a much deeper resonance for it. Oh, yes. Buy the book. It’s that good.
My method is to not explicitly borrow anything, but to set up resonances. If a culture has names that sound vaguely Celtic, they’ll have cultural patterns that follow the appropriate Celtic model, and their history will have echoes of one of the Celtic nations. Similarly English-y names will go with an English-y culture and an English-y kind of history. If I want it really alien, I’ll use patterns that I’ve built myself and build in stressors to the culture that force it in a direction likely readers will find very unfamiliar. What I’m doing is letting people’s subconscious pattern-recognition do the heavy lifting for me – and I have no shame about this. If there’s something that’s not likely to be in the common view of “what medieval English life was like” (as an example), I’ll do the groundwork so it doesn’t surprise Joe Reader too much. Otherwise the general idea, however incorrect it is, is enough to give the feel of something bigger.
Yes. I admit it. I use tropes and collective ignorance to hook my readers and leave them with something a bit more than they expected. Go thou oh lazy writer, and do thee likewise.