There's an elegant method for putting together a quick adventure precis, invented by a clever chap named Steve Darlington. It was intended for episodic format campaigns (and was designed for Buffy games, come to that), and to a degree, it helps if you look at this like you were scripting an ep of a TV sitcom. So, okay. Use the following format:
Song: Think of a favorite, evocative song. Put it right here. Now think about the song, its lyrics, its mood, and see if based on that inspiration you can fill in the rest ...
Hook: What would the trailer for the episode portray as a teaser? This can usually be described in a sentence or two.
Problem: This is a paragraph which describes, in more detail, the situation the PCs are expected to solve ...
Complications: ... and the barriers which are in the PCs' path. This not only includes the Big Bad of the
Resolutions: How do the PCs solve the problem?
Fun Stuff: Many adventures work best with a little comedy (or at least lightheartedness); this is where you put it in. Bumbling NPCs are classic, of course.
Themes: Pure high-concept; what would your advertising tagline be?
So let me run through an example for you. I originally did a bunch of eps for my limited-run Firefly campaign based on Moody Blues songs, and here's one ported over to fantasy:
Song: Legend of a Mind (Timothy Leary’s Dead)
Hook: The village Sensimil in Altania's got the best, I mean the best dreamdrowse anywhere, and a lot of folks like them a good bowl of it to see the vast universes Beyond. So there your band of smugglers is trading, but the village has a bandit problem ...
Problem: The village elders pitch this not so much the party eradicating the bandits as training the villagers up to do it themselves, and if you help them out there’s an extra couple sacks in it for you. Now as it happens the village is quite well-off through the trade, and they’ve got a startling amount of military gear: the best of weapons and armor, crossbows, heaps of bolts, and even some war chariots and ballistae.
Complications: Think 1960s commune; the villagers just can’t wrap their heads around violence. They’re none of them good shots, they think military discipline’s a bit silly, and they’ve all got stab fright. Intellectually they know what needs doing, but in their guts they shrink from it, and it’ll become pretty apparent pretty quickly that the party’s going to have to hunt down the bandits themselves. That being said, most of that fancy gear is still in the packing bundles, new and glistening with oil -- and how did they get what’s plainly Fifth Legion arms? -- and needs going over and straightening out.
There are just a dozen bandits, but they’re bushwhackers and are not just going to sit fat and happy for the party to ambush. They’ve no qualms about retreating to prepared strong points. Play them exactly as cannily as if they were the party and the villagers were the bad guys ... for instance, all that nifty gear’s in a single storehouse with nothing more than a padlock to keep the kids away. Moreover, two of their number are ex-locals with a bit more sand than the villagers, and the village headwoman’s grandson is their inside mole (he thinks the bandit leader is dashing and cute). The bandits’ goal is to cow the village into submission so they can take over.
Resolutions: Whack out the bandits; it’d be more impressive if the villagers do so. Pray the local government doesn’t find out the weapons and armor, which were hijacked from the Fifth's legionary encampment five years ago and unmistakeably bear its scorpion-and-spear sigil!
Fun Stuff: It is the villagers’ inalienable custom to be stoned at any time of the night or day, and some of them don’t just stop at the raw dreamdrowse, there's a plant wizard in the village who magically refines the damn stuff. Leave them to their own devices for long enough and they won’t be able to fire an arrow because the colors of the fletchings clash with their hallucinations. Sitting around in a circle, clasping hands, and chanting mantras while their platoon leader turns a prayer wheel five minutes before a battle is by no means out of character.
Themes: He’ll take you up, he’ll bring you down, he’ll plant your feet back firmly on the ground.
And there you have it. I ran the villagers as Rastafarians (a subculture unfamiliar to my players), lingo and practices tossed in, and they were damn near ready to burn the place to the ground out of vexation by the end of the adventure. I loved it.