It's been forever since my last Tip. I have an excuse, though: My life has been crazy. Anyways, my last two tips have been on World Building, and I think I'll cover the last part of world building today: Culture.
Culture is how your people live their lives and interact with one another. It governs their birth, their marriage, their death.
All in all, it's very important.
You can break Culture down into three basic parts: Religion, Politics, and Survival. However, these very often overlap or even combine. It can be used to govern their surroundings, or the surroundings may govern it. Culture is a very tricky thing.
I like to define the religion of my world first (Something I failed to do with Bookania ...) - I like to know how they view God. Now, they don't necessarily have to follow the true God, or even a God at all, or perhaps they "Have a form of godliness, but deny the power thereof." You must decide. If they don't follow the true God, is there someone who does who can bring him to them? Why don't they follow him?
If you are going to do a parallel to Chrisianity, then I sujest that you study the Bible for clues as to how to do that. For instance, in Bookania,God is called the Author because of the verse where Jesus is described as the Author and finisher of our faith (as well as the fact that it went really well with the name Bookania). In the Rowa, he's called Yshew, because the Hebrew form of Jesus is Yeshua (Which can also be translated Joshua, incidently.) Another common thing I see is forms of the name Elohim. A study of Exodus, Leviticus and Numbers can give you ideas for worship traditions and festivals.
You'll also want to decide how you're going to handle Jesus. Will you do something similar to Aslan in Narnia, or will you simply use God. I've done it both ways. This is something I would pray over, and see how it would effect the plot. The Rowa doesn't have Jesus, only Yshew, but they do have salvation. The focus of Infiltration was the fact that the world is trying to infiltrate the church, and I concluded that to create a Jesus character would simply be confusing and distracting. In The New Division, however, I have Salv. The New Division is about how Jesus' death changed the division from Jew and Gentile to Believer and unbeliever, so having a Jesus character is important.
Once you have the religion mostly figured out, I would mess with survival. What do they have to survive and what do they need to survive. For instance, a people group in a desert would probably have a less advanced culture than someone who lived in a rich every-thing-you-need-is-provided valley. People in the desert have to devote more of their time to the gathering of food and water and the fending off of predators and therefore don't have enough time to develop technologies and build long-lasting structures. The people in the valley would be in a highly contested-for location, and would have to build fortresses and the like to fend off enemies would would like that bit of real estate.
However, the opposite might be the case if someone in the desert people's history had managed to discover or invent something that would somehow make the desert fertile. Then they might have a more advanced culture as they strove to make all sorts of inventions and such to make the place as inhabital as possible. The people in the valley might not have any enemies to speak of, so they might just live in in thatch huts and eat berries all day long.
The last part is politics - how things play out among the uppity-ups. No society can exist without someone being in charge, so you must decide who is in charge. Will it be a king? A president? The oldest person in the community? What sort of laws do your people have to follow? Are there any strange ones? What are the punishments? Any of them cruel and unusual? Do you have a dystopia? This is something you must decide!
I, again, suggest a you read the aforementioned books of the Bible - especially if your people is Christian. I would also suggest a good look at the governments of the past. You can get a slew of ideas from there.
And that's all I have to say for now. If you have anything you would like to add, feel free to comment below. Also, if you have a topic you would like me to write about, feel to comment with a request for that as well.