In the course of writing a fantasy or science fiction story, the subject of alien cultures inevitably raises its head. The reader expects them and so as the writer it is your job to design some good ones. So, where to start? How do I design a culture that is alien enough and that the reader will enjoy? Read on and start taking notes.
Before you can design the culture, you must first decide what the aliens will look like. Remember, not all sentient creatures out there are Human, or even humanoid. So start by deciding what the critters will look like, details of heir physiology, how they eat, etc. The design of the alien must be functional as well as unique looking. Of course, you could always stay with humans, in which case let’s move on.
Next is their environment. How a culture develops is in large part dictated by their environment. For example. Desert people will need to dress in such a way to protect themselves from the sun and preserve their body’s moisture. This can lead to lots of layers of clothing, coverings for head and face, which could evolve into a cultural habit even when away from the desert. In contrast, someone from the jungle doesn’t have to worry about dehydration and so would minimize clothing, leading to a society more used to full or partial nudity, which in turn could lead to less sexual separation at such places as bathrooms.
Then if you have a non-Human race, how their physiology interacts with their environment will also dictate some cultural norms. A winged species, for instance, would prefer their homes in the mountains, high peaks from which they can leap and fly away. Mountains imply caves, so their cities could be a series of caves linked via walkways carved straight out of the mountain. In fact, in all cases the combination of environment along with the physical form of the race will show you what their cities should be like. Desert dwellers might build theirs of available stone, entirely enclosed and roofed to protect from the hot winds, of even in underground caves to better stay out of the heat. Jungle dwellers might build tall wooden walls (since the trees are available) to protect from predators, or if it is a race that can, say, telepathically communicate with and control animals then they would have no fear of predators and so forgo the walls and be more open.
From here we can now determine other aspects of their culture. Greeting one another, for instance. If they come from a rough environment, or are a species more prone to lying and killing one another, then greetings would be approached more cautiously, perhaps cloaked in a ritual originally derived from what amounts to searching one another for weapons. Or the telepathic jungle dwellers, for instance; they would greet strangers more openly. Why? Well, when you can send a mind-call to the local tigers, or if you can pick up surface thoughts from the visitors, then what is to fear?
A culture also has its art. Dance amongst desert dwellers might develop from the shifting-sliding step they might need to walk through the sands, jungle dwellers might have dance routines inspired by how they see the monkeys swing through the trees, while winged creatures would actually dance in flight up in the air. But more than just dance; at this point you can start dreaming up any artform based on cultural adaptations, including nothing like we have on Earth.
Some aspects of a race’s culture might also stem back from something in their history. Was their a devastating war a thousand years back that everyone forgot about? Then that might be the reason why even the young are trained with weapons. A great flood from centuries back would be the reason why houses are built on stilts, then centuries later as they achieve technology they might still be building houses on greatly raised foundations.
Religion is also a part of culture, or the more generalized cultural Ritual. Historically, religions have been inspired by the environment the culture grew up in, mixed in with some of their history. A race long abused by a more powerful culture, might develop a religion based on the concept of a coming savior, which in time would generalize from their need for a physical savior to something more esoteric. Or a race that has only known peace might stay away from the active worshiping of deities and be more oriented towards a philosophy of living.
Often what starts out as a tradition or ritual based on a practical need for survival can long outlive its original need, developing into artful or cultural variations whose origins have long ben forgotten about. As a real life example, the tradition of Arab women keeping their faces covered probably originally developed from the need for keeping wind-blown sand out of their faces, a need now not so great with the development of more modern ways of living and building good solid homes.
Just remember, that a culture comes out from the logic of how a species appears, their physiology, how and what they eat, and their interaction with their environment and their history. From there it is just a matter of finding places for your own variations, then deciding how it might have developed over time, what it looks like at a point long since removed from its origin at the beginning of their history. To develop a culture, start with the seed of what they look like and where they live, then just develop it point by point using logic and a bit of imagination.
How well does this work? In my own “Maldene” series, I have an entire alien world- having absolutely nothing to do with Earth- within which is a variety of different cultures akin to what you would expect from our own real life world.