Economics and Politics
Economic and political theories can be simplified (for purposes of storytelling) to some VERY simple statements: Economics are a rule of who has what, who needs what, and how do they get it there. If someone doesnt have something they need, they will go get it, however they can. Politics are a kind of advanced form of economics in which major players and groups work to get what they want or need.
If you are writing a novel about economic theory or a novel that is designed to promote or exemplify a particular political viewpoint, then this simplistic explanation is probably not going to be very satisfying. But that's all right-- chances are, if you're writing that kind of book, you don't need this writing exercise anyway, because the economic and political elements of your story are so important, it would be reckless to only spend 15 minutes on them.
For the rest of us, those of us who need our socio-economic/political themes to remain in the background, the above explanation forms a really solid ground for making some decisions. But don't just brush today's exercise aside; even the most hack-and-slash sword-and-sorcery story can benefit from a little behind-the-scenes intrigue.
The most important decision, of course, is what kind of resources your people need, and where those resources are. Farmland is an obvious natural resource that most cultures need (though "farmland" can also be extrapolated to "food-raising land" in cases of heavy meat-eaters and hunter-heavy, often nomadic, societies). Water is another-- you cannot have a living civilization without water. If you look at the political scene in the Western United States, you can trace nearly every major political decision involving land back to water. Who has it, who doesn't, and how can those who don't have it get it.
But food and water aren't the only important resources. Timber and stone are important for shelters. Salt is vital for life.
Certain types of minerals are more valuable than others-- like diamonds versus granite. Granite is more useful for building things, but diamonds are more precious. Some minerals are not useful until technology advances to a point where they can be made useful-- as with boron, an element that isn't tremendously helpful until it's turned into borox, which was used heavily as a cleanser and an effective (though later found to be toxic to pets) pesticide.
If you have a magic-rich world, there may be resources not listed here that are important to your world. In Mercedes Lackey's Valdemar series, special "ley lines" of magic flow through the world, and where they meet up, magic is stronger and more powerful magics are possible; the redistribution of that ley line magic resource is the major struggle in the last series, the Winds of Change books. Personally, I like to see the struggle for a missing resource as a motivation for characters (villains especially). It's much more satisfying to encounter an ambitious land-grabbing villain who wants all the land so he can rule, than just someone who's evil and nasty because he's evil. "Because he's evil' is a fine reason in some books, but it doesn't hold up well to scrutiny.
Don't underestimate the power of the human imagination in developing your list of resources, either. Jerusalem is a city which is well-placed in terms of its nearby resources, but far more natural-resource-rich areas exist. Still, civilizations have been fighting over this one city for millenia-- why? Because it is considered sacred. There cannot be very many such sites in your world, because eventually, people will decide they're not worth losing so many lives. But a few key sites can in fact become "hot spots" of an imagined resource-- something that may or may not have much intrinsic value, but its sentimental value is extreme.
Just as you examined your timeline for events and pressures,now examine your map for resources and deficits. For five minutes, make a few notes on the map to mark places that have more of a type of resource, and jot down anywhere that has a definite deficit of something needed. Also check your timeline; some of your pressure-point conflicts in the last 100 years may have resulted from an unexpected increase or decrease in the resources of one area or another.
When you're done with the resources, take another ten minutes and identify which major groups in your civilizations care about which resources. These factions may appear in your story-- they may be opposing the hero(es), or even helping the villain, or they might help the hero or at least get out of the way, depending on how each faction perceives and responds to the various characters in your story. If you are aiming for a political story, you'll want to flesh this out with descriptions of how the factions perceive each other as well as the hero and villain, key people in the factions, and their tactics in dealing with others. Again, feel free to label these with generic names for now; language is coming soon!