There is a great article on IO9 (part of Gizmodo) on making worlds that are believable. It’s an excellent read and something I think everyone in speculative fiction should read. But how do you build the worlds to start with? As with anything, you start with concept. In this case, what role is the world going to play in your story?
If this is where someone is from, then why? People don’t typically just up-and-leave one place for another…there is almost always a reason. So, what caused your character to decide they were going to move from there they were to where your story is? (This is also some good ammunition for your character’s backstory if you play it right.)
If this is the setting of your story, why is the sociopolitical situation like it is? How do the elite view the situation? What about the common people? Keep in mind that any society, save, perhaps, a hive-like society, is a society of individuals, each of which has their own views that don’t completely match the views of the person next to them. The Than-Thre-Kull of the series Andromeda may have been a hive mind at some point, given the quote, “My life, my soul, for the hive, for the hive” said by Lieutenant First Class Refractions at Dawn in “Under the Night” and even they had independent thoughts. So think what the prevailing sentiment is, but also consider what individuals who interact have to say.
Next, consider the basic history, how did they end up where they are? The history gives enough of an indication of why things are the way they are that the reader (or viewer, if your work is a screenplay) gets to observe. The more directly involved in the story the world is, the more you have to consider the history, people, and interacting cultures. (This includes infrastructure, and other things.)
My world creation starts with the characters, the major players of the story. I look at where they are from, and start expanding from there. This means that the worlds could be literal worlds, such as those in Elizabeth Moon’s “Vatta’s War” series, entire star systems or collections of star systems such as the many systems and governments of David Webber’s “Honor Harrington” series, or even different cities and countries on a single world. (Having traveled from Dallas, Texas, USA to Daiba, Tokyo, Japan showed me how we may exist on the same planet, but Japan is worlds apart from America.)
From the characters, I look at how the characters’ societies came to be. Societies are as complex, perhaps more so, than the individual people in those societies. Then I look at how the society affected the characters and how they are treated by the society. This can also bring in some interesting challenges for the characters too. Let’s look at Firefly. Captain Malcolm Reynolds and his first officer Zoe fought in the civil war as an independent…but his side lost. So, in the time that the series actually takes place, there are several points where that background is reflected in society. In “Bushwhacked,” Commander Harken makes several references to Mal’s past, and in “The Train Job,” the writers put Mal and Zoe in an Alliance bar on the holiday celebrating the fall of the independence and the unification of the worlds. Those are some obvious references to their past, but there’s more subtle ones too, especially in how those two characters interact with people outside their ship.
The final piece is I look at the individual views on the players in the story (major characters and reactions) plus the overall views. This is somewhat distinct from the society, as this is on the individual level rather than the societal level. Let’s say you have an inter-racial relationship, where you have an individual who views this with distain, but society views it as acceptable. Someone on the street may give a slightly disdainful look at the couple, but may avoid incurring a societal repercussion by not saying anything. This individual decision is what makes them separate from the cookie cutter. Now, say that society frowns on the inter-racial relationship, and one person doesn’t really love the other but is in the relationship to push against society. Again, an individual decision that separates the person from society. The first is the person outwardly acting within societal norms while the second is outwardly defying societal norms, and each has their own reasons for taking the actions they are taking. That’s what makes them different.
I also think about the mundane. What is the expected day in that society? What about the character’s expected day? What if that is disrupted? How do they handle bathrooms? What about trash? Bills? Groceries, food, et cetera? Medicine? Castes? Crime? At this point, I’m thinking of such low level stuff that the world is starting to have a life of its own…as it should be. When I can see it, hear it, feel it, smell it, and taste it in my head, regardless of how big or small the world is, then I have a world. It’s only a matter of letting hints of this show in the story so that my reader can be there…at least for a while.