Try not to Cut and Paste Cultures
Now, this is one of the hardest things for a Fantasy writer. A lot of what is considered, shall we say “typical” for the fantasy genre comes from a British/Celtic/Western European template. It’s not unavoidable, but it’s damn hard to avoid completely. In no way do I claim innocence. I’ve had it noted that many aspects of Druth culture come off as “VERY British”. One workshop reader of Holver Alley Crew told me she thought I was British until she actually met me. So this is something I struggle with.
There’s two key reasons why it’s so hard not to do. One is it is damn difficult to come up with a culture, with every element of clothes, food, social mores, government, religion, architecture, etc., etc. out of whole cloth. The second is the need to give your readers something recognizable they can grasp onto to get into the story. You could make a culture that really is nothing like anything every seen on Earth… but would your readers really understand it? Or would it be so alien that it would be impenetrable?
I think the real key is finding that balance between the familiar and the unique. Familiar enough not to lose the audience, unique enough not to bore them. You can have cultures that suggest similarities to Western Europe, Eastern Europe, Arabia, India, China, Japan, Africa, Mesoamerica, Polynesia, etc., etc… but should avoid making them such obvious copies that people don’t look for anything deeper.
Of course, if one is writing Urban Fantasy, or Alt-Earth Fantasy, then these don’t apply.