A lot of these can be thought up by just walking around.
About the land, it usually involves geography of the land, is it hilly, mountainous, flat. How easy is it to walk there. What flora and fauna is there. How dangerous is the place for the average person, etc. Basically, just walk through a part of the city. Whatever your thoughts on it, can be the setup for the land you want to write about. It is impossible for you not to have any thoughts about the parts of the land you walk about, you just don't realize that you are actually forming an opinion of that place. Write that down.
As for cultures, these too can be thought up by just walking around. Some people spit on the ground? That could be one part of the culture of one group of people in your story. You see someone arguing, that's an idea right there. You see someone stepping on dog poop, that's another idea. So now you have a group of people called the Masingi (first word that came up in Ai-chan's head) who are a disgusting group of creatures who trail spit wherever they go, loves to pick fights and is so clumsy and stupid to the point that they don't realize they've made themselves enemies everywhere.
