For me, it's a mixture of things. I start first with the World itself.
How big do I want it? World-size with multiple countries? Universe-size with multiple planets? City-sized with a bunch of factions? I define these details first because it sets the "Board". I don't define everything on the Board, but it keeps me aware that I will have to eventually.
Then, on that Board, I put my MC and begin to place the Pieces. I define who they are directly influenced by, who they will interact with regularly, their backstory, and their life, and I define all of the information pertinent to completing their "Bubble".
Then, I work on the side characters. Not a whole lot, but enough to fill in the gray areas. I outline what is "known", what is "to be known", and what is "never known but felt".
- Known is everything known by the MC at the moment we start the adventure.
- To be known is everything that will eventually be known by the MC. It may not be known now but will by the end of the story.
- Never known but felt means that the MC will never know, but the character is influenced by these details in the background.
Next, I define where the Character will inevitably go next up to three stops, just so I can get ahead a bit and start planning the direction of the story I want to go. I outline the characters there in those places, outline the "why" the character is going there, outline what he may/will do, and outline the same three things. Known, to be known, and never known but felt.
I generally don't outline every single thing in the world at the start. Doing so puts you in a box and you can actually waste time if you decide to change things later on, but you do want to set up a list of "Rules" that the world follows. Set standards that will be the same everywhere. I.e; if it's fantasy, then there's probably a Guild in every place the character can go to for information. Simple things to help you stick to the boundaries of your story and maintain its realism of it. Don't want to accidentally break character and break your own world, do you?
After that, I flex and adjust. My characters grow with the story so how they approach the next stop will always be changing until they actually get there. And I'm a different writer than usual. My outline is actually very slim and changes with every chapter, as I'm the type that throws stuff at my MC and then decides how they will face the problem in the moment. It helps bring a bit of realism to my stories. I do have an end goal and I do set up what I want to happen along the way, but I'm very fluid with it. Until I hit that send button, anything and everything is fair game. Even my MC's life is just a dice roll away from being ended if the story dictates that it's time to go.
We don't go through life knowing everything that's going to happen every day, and I write in the same way.
Worldbuilding takes practice and everyone has a unique style. Feel free to experiment with a bunch of different techniques and see what helps you! Some people start with characters, others start with outright maps. I like to start with figuring out the scale of the story I'd like to write.
Best of luck!
-- J.C
Edit: I did fail to mention how I plan out the Locations and actually focused more on the characters. Kind of side-tracked myself.
When it comes to locations, I put effort into first defining the Culture. What's the "norm"? I define clothing style, language, races around in the area, and I also look at my map to see where the location is placed. Is it a trading hub? Is it on the outskirts of the known world? Is there a dangerous forest/labyrinth nearby? All of these details will influence foot traffic, the security levels, the size of the location, and even the way everyone dresses. Dangerous places will likely be more "guard-heavy" IF that's the culture. If it's a slums/cyberpunk city where thugs rule, then guards and police will certainly be minimal here.
If it's a country, I look at the location of it on the map. Countries with more beaches/ports will be more fish and trade heavy. They'll probably have plenty of tourists and lots of money in those beachy-areas. Mountainous locations will be poorer and less dense population wise. The people will be tougher, grittier, and less up to dealing with the bullshit. If a country is a warring state, you better believe there's a lot of guards and more militant-like air. If it's a magic-based country, then it's probably more "advanced" in magic-stuff. Expect more fancy things to be around in the cities and villages.
If I'm going Universe-sized, then the planets will follow similar rules. I use Halo as a big example for this. Some planets will be trading hubs, some big shipping yards. Others, like Harvest, will just be agricultural farms. Some planets will be rebel/thug hideaways with asteroid belts full of pirate ships ready to steal the goods of the unlikely vessels. Police ships will be patroling, but likely thin around those darker spaces.
Some general rules can help steer you in the direction of what you should be doing. Follow "common sense" and then go from there to make it unique to your own story.
