One of the hardest things to do when writing is to build actual culture into your world. When you are trying to tell a story and are limited by the number of pages that you can use (or that your reader is willing to read) you have to walk a careful balance between world-building and storytelling. Too much world building means that you lose track of the plot, too little and the world feels flat and shallow. I am by no means an expert when it comes to walking this thin line. When I was working on my undergrad, I majored in Human Geography which is the study of cultural groups. I can write about culture to the point that most readers will want to gouge their eyes out because I find it fascinating. My wife, bless her, usually suffers through reading my first drafts and tells me when I am focusing too much on world building and not enough on plot. The first drafts of Wolves were notoriously bad about this in part because I was very heavy-handed with cultural aspects but also because as a combat veteran and former artillery officer I can talk ad nauseum about weaponry and battle formations (enough to make David Weber, Eric Flint, and David Drake throw the book across the room in frustration). Finally, though I hit upon a technique that has helped me a great deal to walk that delicate balance. I thought about the video games that I enjoy the most such as; Mass Effect, Horizon Zero Dawn, The Last of US, Tomb Raider, Detroit: Become Human, etc.
All these games do a fantastic job at establishing culture, and they do it through small details which are often simply part of the background. So, I took a page from them and have started trying to build cultural elements through quick mentions of things that the reader’s mind can file away as background information as opposed to heavy world building. The best example I can give is that in Wolves, the nurses in the army medical units carry small twin barreled pistols with the words “mercy” and “peace” carved in them. That is to give those soldiers that are too far gone to save (or themselves at times) mercy or peace through a mercy kill. That small tidbit, especially when mentioned several times does a lot to establish the cultural mores of the world without devolving into a philosophical treatise.
The other technique which has taken me quite a bit of practice to get any good at is trying to introduce cultural elements through dialogue between characters. Again, I am by no means an expert, but if you had read the original draft of Those Below(Which I buried with a stake through its heart) I had entire chapters of world building with no dialogue or character interaction which essentially read like your high school history textbook, that is dry and boring. It did not work. However, I again turned to video games as an example (especially Mass Effect). In these games, you could spend hours reading journal entries and lore (which admittedly I frequently do because I am a nerd) or you can pick up enough to fill out the world through the dialogue with other characters. On my rewrite of Those Below, the characters of Misi, Achachila, and Mantaqway became vital as tools to create a cultural reference. Their interactions were often less critical for moving the story forward but could be expanded to explain cultural phenomena.
My advice to any new author would be to find little tricks, such as these, to try and build in those critical cultural elements. It is critical if you do not want your book to feel flat and underdeveloped. Think of your favorite books, and I guarantee that beyond a fantastic plot all of them have fully developed worlds. When you write, make sure that you would want to read what you are writing. If it feels flat to you then, unfortunately, it probably is, and you may need to start over. I had to restart Those Blow roughly eight times before I got it to take. Anyway, just some thoughts on my own development as a writer, hope they help.