Often times you’ll find a need for a foreign culture in your writing. But you can convey a sense of a vibrant, multicultural world without having to delve into the minutiae and idiosyncrasies of every nation. It’s fine to flesh out nationalities and ethnicities that recur or play major roles in your story. But don’t bog readers down with information that doesn’t help the story. And once you’re at peace with leaving out those details in the story, you’re free not to develop those low-level details.
So what’s the shortcut that will let you build a culture is just five minutes? R.E.P.A.R.
How are the people of this culture known throughout the world. Are they merchants or craftsman, warmongers or peacemakers? This doesn’t have to be a fair generalization or even an accurate one. It should be the one that the protagonist (or his people in general) would hold about this culture.
What are people from this land known for? If this culture has trade contact with the locale in your story, odds are that they are associated with a particular export. Maybe they are fabled vintners or silversmiths. Perhaps they supply a much needed staple, such as grain or cattle. Seeing a person from that culture on the streets might prompt thoughts of their people’s most famous products.
Who are these people relative to the residents of your protagonist’s homeland? Are they friend, foe, or neutral party? Do they have the same sort of government, or some strange, foreign means of leadership that seem quaint, bizarre, or nonsensical to the locals? Unless most people are ignorant of the culture in question, they should have some opinions about the politics there, even if it’s a simple one.
Pick an adjective that someone from your story would use to describe a person of this culture. It should be something that a local would use to easily distinguish someone of the culture you’re describing. Are they notably tall, light-skinned, or dark haired? Do they dress outlandishly? Do they have a particular accent when speaking the local language? Pick out a trait that would seem most prominent to someone of the dominant local culture. It may not even be an accurate description of the culture in question, but these sort of broad-brush descriptions are commonplace anyway.
Who or what does this culture (usually) worship? Focus on the main differences in belief between this culture and the dominant culture. Do they worship the same god, just in a different way? Do they revere another god or gods from the same pantheon? Maybe they have another system of belief entirely, possibly one that is misunderstood or mischaracterized this culture’s beliefs.
The Azonid people are fearsome warriors. They trade the spoils of their wars for staples such as rice and barley. Luckily, they have been allies since the Seventh War, fighting alongside our brave knights. You can pick out an Azonid by the fur hides they wear, and their habit of braiding the hair of their beards. While they hold our patron god Felmaa in high regard, they owe their allegiance to Dornan, the Divine General.
This sort of cultural sketch is enough to pepper in minor characters that make a story seem bigger than the words on a page.