This is more along the lines of fantasy or dystopian writing.
If you are creating a world, make it (or part of it) ugly, dirty, and creepy. Think of a big city, you know that one spot that everybody hates to go to? That is a great place to write and create, because you can do whatever you want to do with it. If you write about a place clean and posh, then you have a certain lifestyle to write about; dirty places can be very diverse.
If you want a place that has a lot of murder, make it either a really big city or a very small town. If you want a place with a lot of poverty, I would suggest a city. A small town or a city are both great for writing about drugs and criminals (hence my book series 'Helena'). These are all very dirty places to write about, and to create.
Make it ugly, but keep it clean. The most common thing in fantasy or dystopian is rebellion, therefore put a character that doesn't fit into that dirty society into that place. Make them wreck havoc, but then make them feel the consciences of it later on. It came make a great plot.
this is where i ramble; have fun