I try to develop architecture, clothing, lifestyle, religion, and language.
The biggest part is the environment. For example, with a desert people, there are some things to note:
Sun protection - clothing covers the whole body, and is light to keep people cool (like traditional Arab dress)
Horse or camel culture (especially if nomadic in origin) - pants, especially for men (from cavalry soldiers) like traditional Steppe, Persian dress
Little water and food supply - smaller villages, nomads, large population centres are around any lakes, rivers (especially deltas) and seasides
Natural vegetation - likely few trees, most available plants are reeds and such by rivers, therefor housing would be primarily mud walls, wicker, leather, and stone (mostly the wealthy or for military structures)
Architecture - smaller buildings, close together - most people don't have plots of farmland separating the houses
Walls - none, open landscape makes for far vision, distant villages, only walls are made to keep livestock or mounts together - except for forts/castles
Climate - relating to earth, people often worship the sun when it is a powerful force, and pray to the gods for rain when they live in areas that lack it. With most boating having to do with fishing, and the area not having lots of islands, water gods like Neptune would be unpopular. So we develop our religion true to that
Then;
Religion - for a people like Muslims, where idoltry has been forbidden, architectural design goes away from the statues, gargoyles, paintings, and mosaics that we see in France. Rather, their buildings would rely on unique architectural elements, such as domes, fanciful edges, towers, ornamental pools and gardens, and colourful stones for mosaics of abstract design.
Language is really random - there doesn't seem to be an environmental connection for this; languages are more about the migration patterns and dominance of certain civilizations
So just from analyzing the environment and a few other things, we can draw a bunch of ideas for the culture that seem very reasonable to the reader.
We probably shouldn't have a Sun-worshipping clan of half-naked people living in stone houses in a remote wooded area with a climate like Norway.