Lots of fantasy and sci-fi writers have workshops about world building and how to make your imaginary places truly come to life. I highly recommend Googling if you’re looking for comprehensive guides to world building.
My secret to building believable worlds is pretty simple:
Relate it to the character.
Take the opening lines to Cold the Night, Fast the Wolves:
I’m not one to run from a fight. But when I’m outnumbered and a storm is brewing, I’m not going to be a chump either. Storms on Tundar only mean more ice and near instant death from hypothermia.
The main character, Sena, is running from some bad guys when this scene opens. I include the descriptions about the storms to set up the world around Sena while also adding urgency — she needs to run because there’s more danger than just the bad guys coming to get her. But at the same time, I’m also telling the reader what her world is like: if you get stuck outside here during a storm, you’ll freeze to death.
There were multiple ways I could’ve described the ice and the storms while writing. I could’ve written more about what the storms feel like or look like. But I didn’t want to break the action. My character is in the midst of running away from bad guys and wouldn’t stop to think about the storms in too much detail because that would be dumb and distracting for her AND because she already knows about the storms. She grew up on this world.
So, whenever I introduce details about the world, I phrase them in such a way that they come across as normal insights from the character, rather than a long description from the author. This makes the world building seem natural and seamless for readers.
I hope you try this out in your own writing. Tie the elements you’re introducing to how your character would see the world around them. Relate it to them—and your readers will follow!