So You Want To/Avoid the Theme Park Version
Step one: Do some research.
If you try to write about an existing place, or base your creation off of a real place, either go there (for more than one day) or find out as much about that place as you can. The second one especially counts if it's in a different country. What's different? What's the same? What makes the place unique? What's probably similar to what you already know?
Try to capture the feel of it while still writing about it as if it was a place like any other you've described. After all, if all is well, it's still more or less in the same dimension, experienced by the same or similar people as the other places.
Don't stuff in everything you think you know, keep it subtle. Do the people in the place you live in constantly shout about what makes them different from the rest of the world? Not likely.
These things also count if you're writing about a completely imaginary scape, especially a pre-existing one, but the difference is that you often can find out everything known about the imaginary place as opposed to the real one.
Step two: Humans are human.
They won't be some musical robot-hobos in weird rainbow costumes. So write 'em like they're human. They won't all look or act the same, even if they share some traits. Some may not understand your protagonist when spoken to. Some, correction, many, won't really care if he's there or not. This especially counts if your protagonist is ordinary dude #3879 in another country as opposed to another universe or timeline or other such place where he would actually stand out. No, crazy foreigners won't all wear lederhosen, except maybe for the mumbly guy on the funny smelling corner, or iddunno, that guy who goes to some folkloric party.
There will be laws and customs different from what your character is used to. But honestly, you won't be forced into them. (Except maybe the laws, but those often make sense.)
The thing with people in weird costumes that act weird on top is this: They either get paid to do so, it's a special occasion, they're crazier than the mean or they do it because they think it is required.
However, most will dress and behave in accordance with their culture's expectations and mores. A custom may be weird to an outsider, but it isn't to the people who live with it everyday. If it's customary in your setting for men over the age of fifteen to wear a hat shaped like a teapot, the weird one is going to be the guy who doesn't.
Step three: Two sides for everything is the minimum, whether this everything be conflict, place or person. In this world, there are at least seven billion points of view on every given moment, as much sides to stories as there are people involved, and let's not start about gender, because you know there are more than the ordinary two. Contrasts and parallels wrapped into the same place. Such is this world's nature.
A city is not just skyscrapers or monumental buildings. A country is not just fields. There are plenty of places in any country most of that country's inhabitants haven't heard of. There are rich parts and poor parts. Places where the clean-up crew is paid to come and places you can't pay the clean-up crew to go. The manic grin of welcome and the axe crazy woobie behind it. Landscape under influence of the blight of the apocalypse and relatively ordinary pieces of nature and world that ensure that life is still possible. Pollyannas may exist on a Crapsack World. Doom and hellfire might still lurk underneath Utopia.
A place, a world, a life is made of pieces. A themepark is merely a piece. So is a bar, the house of a friend, the swan-infested lake, that creepy alley, that one street with the pretty lights when it's foggy, John Smith's farm, the dark forest where people disappear, the village fair, and all the people you meet. Pieces.
Now put them together into a wonderful chaotic, detailed, intricate, complicated world, full of light and shadows and colours. I know you can. You're awesome, remember?