It doesn’t take as much time to construct a whole new world as you believe. It all boils down to some simple rules. Ask questions, investigate the weird stuff, challenge your restrictions, and turn to history when you get stuck.
Ask the Weird Stuff
Imagine you’re the city planner and municipal government for your new city/country/planet. How do things work? Where does refuse and sewage go? You don’t need to describe the sewer system, of course, but this will give you a good idea of how clean and sanitary your city is. FYI, medieval cities were filthy, even by the standards of medieval country folk. Consider if there is magic, if your characters are just used to seeing this, etc.
Wonder who cleans the streets, who makes city-wide sanitation decisions, how much the governing bodies know about disease, and how that may play into your story. How likely are characters to get sick? Small wounds can be a death sentence in places with raw sewage in the streets and contaminated water sources (we’re looking at you, old London town).
In a fantasy, scifi, or horror setting, you can always make the contamination supernatural in some way. Water from a certain well causes all men over forty to drop dead. Lycanthropy may affect any open wound, like bacteria, if a werewolf is breathing nearby. The ideas are endless, and they all start with the weird questions.
Figure out how things work. How does food enter the city? How do people cope with death in this culture? Where do the dead go – in body and spirit? What system of government do regular citizens rely on? How do new leaders come to power? Has any of that changed recently? What about clothes? Do people make their own from scratch, sew their own from bought cloth, buy premade apparel, or pay for custom work? Is there a class system that influences these things? Are those classes flexible? How did they come to be?
Ask yourself about soap, shampoo, lotion, makeup, perfumes, high art, street art, public drinking habits, private drinking habits, etc. How do people get around? What are practical reasons people avoid dangerous areas (that you will inevitably force your heroes to go)? There may be a monster in the bog, but more people would die of malaria or dengue fever.
Try the Personal Approach
Stop and look at your life. What irritates you? Is it your commute? Do you just hate shopping? Maybe laundry is the worst chore in the world. When you build a new universe, feel free to address personal frustrations. Build the culture around your frustrations. Highlight them or find a cultural excuse to avoid them. Maybe your character suffers with swollen and cracked skin after doing laundry the old fashioned way. A culture may only do laundry once or twice a year to preserve water and have extensive wardrobes instead. If you feel strongly about something, you can write with greater gusto about it.
Don’t Fear the Gods
This is a short note. By now, all world builders know religion is important – one way or another. The easy way out is to pit a culture with a pantheon of deities (often that mimic Norse, Celtic, Egyptian, or Greek mythologies) against a monotheistic culture (typically something that looks an awful lot like Christianity or Islam). Personally, I find this a bit lazy.
Fictional gods are only as real as any other fictional characters you create. Be creative and have fun. Give cultures two gods, dozens of gods, or no gods at all. Just make sure you make them unique. Your characters deserve a rich mythology (or twenty).
Open Up the History Books
Your high school textbooks may help spark a few ideas, but frankly: you’re too familiar with them. Even if there is a great idea hidden in a battle of the Civil War, you may pass right over it. Go for a different kind of history. Break out the weird textbooks. Even better, crack open some history texts from other cultures and parts of the world you aren’t as familiar with. Dig deep, follow your nose, and you’ll find all kinds of secrets buried in our collective past. It’s surprising how different our own ancestors were. Their culture can inform yours.
Get building! Your world can be as vast and rich as you want. The only limit is your ability to ask questions, dig into history, and wonder about the weird things.