I recently attended the World Science Fiction Convention, and one of the panels I was on was about Faith in Fiction -- how something that's been pretty essential to human culture tends to be left out of both world building and character development unless they're central to the plot. That got me started thinking about some other fundamental issues that tend to be neglected unless they play a role in the plot. If you think about these issues, it can add a layer of dimension to your character and your world.
One big thing is the issue of money. An economy is crucial for worldbuilding, but it's also an important part of life for individuals. Money is a major motive for crime, a motivation for many of life's decisions, a major factor in marital and family discord, and yet a character's attitude toward money seldom comes up unless it's important to the story that the person is greedy (like killing for money). Think about how many times a day you have to make financial decisions, spend money, think about spending money, think about not spending money, etc., then think about how often you see fictional characters dealing with this. Not that you want to fill a book with this, but when your character has to deal with money, what's in character?
When you're developing a character, here are some questions to consider:
What kind of financial background does this person have? Did she grow up rich, poor or middle class? How aware was she of her family's finances? Did her parents fight about money? Did she know they had to scrimp and save or did she just get Daddy's credit card?
What is her financial situation now? About what salary would someone with her education and experience make in her field in her city? What are living expenses in that city? How does she adapt to any disparity between living expenses and income? Does she stick to a budget or run up credit card bills?
If a character's financial situation now is different from his past, how does that affect him? Does he still try to live the old way, or does he adapt to his new circumstances?
How does the character feel about debt, credit and savings? Is he a cash or credit card person? How does he pay his bills -- online, in person, by check?
If she sees something she wants that she can't afford right now, what would she do and how would she feel?
What are the character's financial goals?
These are just some things to think about, and there are no "right" or "wrong" answers, only what's right or wrong for the character. For instance, some people who grow up poor but later have money may still be reluctant to spend money, while others become super generous. Their motives may also be individual. One person who's reluctant to spend money may be a miser while another might be afraid of being poor again. The thing is that if you know these things about your character, when the issue of money comes up in the course of your book, you'll know how your character will react, and that can even shape your plot.
This had a lot to do with how the first book in my series, Enchanted, Inc., kicked off. I'd already decided that my heroine was struggling to make it in New York, where her salary wasn't quite enough to cover living in the city, so she lived with two roommates and she tried to make the most of every dollar. She even walked to work as often as possible rather than spending a couple of bucks for a subway ride, since that added up, and it was only because she was running late one fateful morning and decided to splurge on the subway that she discovered the magical world. Her financial situation also helped lead her to being open to considering a mysterious new job. Those plot events might have happened anyway, but knowing how she felt about money helped add a layer of development to her character during those events and, I think, helped ground this fantasy world in reality.