One of the traps a writer can fall into is spending so much time developing a world they feel the need to put as much of that into the story as possible. While it's good to know a lot about your world, the reader usually doesn't need to know everything you came up with. They just want to know what's relevant to the story. It's your job to find that balance.
Understanding your protag's place in that world can go a long way to figuring how much to share. This is important because how your protag moves through this world is how you're going to describe it to the reader. It's also a good way to avoid "world builders disease," the urge to put it all in there.
I like to start by figuring out what a normal day is for my character. That makes it easier to know what you can do to push them out of their comfort zone and what constitutes a bad day for them. Bear in mind that these questions are designed solely to get you thinking. They're not a checklist to fill out or anything. Not all of them will apply to your world or story, but hopefully they'll spark other questions that are more relevant to your world.
How does this affect your protag's daily life? Do they have to worry about it, or is it something that never troubles them? Do they own clothes or gear to protect them from the elements? Is this something that could cause them problems on a regular basis? Are there any ways they can use the weather to their advantage? Could it put them at a disadvantage at any point?
2. Agriculture and Food
How does your protag get food? Do they need to worry about starving or are meals always provided without a thought? Do they have any experience dealing with farming or animals? Are they comfortable around them, or is it a lowly profession? Do they work in this profession? Do they know people who do? Does eating or food play an important role in their life, such as a ritual or an escape, or even a reward? Do they have any attitudes or beliefs about food?
3. Plants and Animals
Is nature a problem for them in any way? Do they know anything about living on the land? Would they know poisonous plants or animals? Do they use it to their advantage? Are they comfortable outdoors? Are they good with animals? Do they fear any animals? Do they have any pets? Does a particular plant or animal hold any significance for them?
4. Economy, Industry and Resources
Where in the overall economic environment do they fit? Do they have a job in any particular industry? Do they know the value of important resources? Do they have access to any of it? Does industry or the economy cause them troubles? Does it aid them? Do they have money or are they always broke? Do they have enough of the basic necessities? Do they have luxuries? What do they consider basic needs and luxuries? How do they see the economic or social structure? Does knowledge of any of these gain them an advantage to the conflict? A disadvantage?
What do they do for fun? What do they like to do in their spare time? What do they find boring? Offensive? Exciting? What activities do they like? Do they participate in any group activities? What do their friends do for fun? Do they approve or disapprove? What do they think is normal vs risky vs boring fun? Does their recreation provide them with a skill that they can use in their conflict?
What's their educational background? Do they feel smart or dumb compared to other people? Are they book smart or street smart? What about their friends? Their colleagues? Do they try to continue their education in some way or just deal with situations as they always have? Do they have any biases toward people with different educations? How do they feel about education in general? Can this be a source for conflict? Can it provide a resource to overcoming a conflict?
Do they follow any particular religion? How devout are they? What about their friends? Do they have any biases toward those of other faiths? How do they feel about the extremes of their religion? Does religion cause them any problems? Can it be a source for conflict? Can it be a source for aid? How much do they think about religion? Participate in region or rituals?
8. Art and Architecture
What kind of style do they have? What do they like? Dislike? Do they have any biases toward a particular look or style? Do they aspire to a particular look or style? Why or why not? Can this play any role in their conflict? Can they use it to aid them in any problems? Does it cause any problems or conflicts?
Now, ask yourself a few basic questions and think about how it relates to your world.
- What is a normal day like for your protag? Your other characters?
- Who are your protag's enemies? (not just the antag, but people who don't like them) What social or economic group do they belong to?
- Who are their friends? What social or economic group do they belong to?
- What are the things your protag tries to avoid on a regular basis?
- What are things they try to get on a regular basis?
- Where do they fit on the social and economic ladder?
- Where do they live?
- Where do they work or go to school?
- What are some challenges living in that world present?
- What are some advantages living in that world present?
By now, you should (hopefully) have a good sense of the world your protag lives in and their role in it. You have enough information to see potential obstacles and ways you can start weaving your plot elements together with your world building elements.
Do your characters help build your world or do you let your world build your characters? Do you have a preference? Which do you do first?