How's that, now? Overarching ideas can be interesting, they can be fun, and they can even be memorable. For example, as a sort of an aside while one of my players is unable to get online I've decided to devise an AD&D setting using a combination of Ravenloft and A Mighty Fortress to create a haunted fantasy version of Langeudoc in the 17th century;. That's a pretty high-concept idea right there, full of weirdness.
Except, if that's all I did then that wouldn't be enough. I can name little french towns until I'm blue in the face, but that will never make them feel French. This is related to the concept that all worlds are alien; and that we must take great care to understand them and not simply assume that we know how people think or act simply because they're people.
If we take a look at some examples, we can see just how important little details are. Then we can talk about what it means to be a little detail; what exactly they are, and how you can add some to your own settings if you like.
First, let's examine our primary source material, that is to say: Greyhawk. Most D&D settings sprang from Greyhawk's loins one way or another, so it's nice to get a look at what makes it so flavorful. It's been derided a lot in the past as simply a "generic" campaign setting, but any setting that has had as much love and devotion put into it as Greyhawk has is anything but generic. If anything it transcends genera to become nearly archetypal.
Let's just crack open TSR 1015 (World of Greyhawk) for a minute and see what we can find. The first interior pages are covered in coats of arms for various kingdoms, cities, and peoples of the Flanaess. Huh, that's not relevant game information really, but it is pretty flavorful. A few pages in we can breath easy because we've found the table of contents. But what do we find there? Here are the chapters:
- Eastern Oerik, Relation, The Whole Oerth & the Heavenly Bodies
- Trees Common to the Flanaess
- A Brief History of Eastern Oerik
- An Examination of Populations
- Characteristics of the Races Inhabiting the Flanaess
- Ancient and Current Languages
- Portentous Runes & Glyphs
- An Overview of Political Divisions
- Geographical Marvels, Regions, & Prominent Features
- Deities of the World of Greyhawk
- Royal & Noble Precedence & General Honorifics (appendix I)
- Social Rank & Hierarchies (Appendix II)
- Heraldry (Inside Covers)
This is a technique that's useful for writing as well. Nothing conveys setting so much as small, insignificant, and often overlooked details. You can transport yourself to an entirely different world based on details alone. What is your ale called, what is the name of the local delicacy, how far is it from here to some strange locale that no peasant has ever visited?
Know the names of your gods, make new names for your coins, name the stars in the heavens and the plants on the earth. Know the drinks in your inns (if there is a trade in drinks), know the holy days of your various religions. Make them up on the fly if you must, only write them down afterwards so you can remember them for next time. Give your setting a set of constant and unchanging truths about it that are different from the truths in our world. These are the keys to evoking strangeness, otherness, fantasy. These are the portals that will transport you to your own world.
Details are what make up everyday life. And if you're attempting to give a picture of everyday life (extraordinary everyday life, perhaps, since you are playing with adventurers and not farmers) then you're going to need to know the pieces that make that life up. The more detailed you can be, the easier it is to transport your audience to a strange world of outlandish customs. Knowing these things isn't necessary to play any version of Dungeons and Dragons... but it enhances the experience.