Here was the first really good one. Spoilers for Keep on the Shadowfell:
[sblock]Situation: Half the PCs were in the Keep, at the mercy of Kalarel.
The Keep:
Kalarel: Submit to the will of Orcus, or die!
Kalarel was trying to break them, to curse them to do the will of Orcus. I started off by using torture, but the PCs were resisting. The Warlock feigned an interest in Orcus to keep the hot pokers away from his flesh, so Kalarel dragged them all to the upper temple. (Room 18)
On the way there, the Fighter broke his bonds.
We're in the blood-soaked altar room. Time for a sacrifice! I started dragging the PCs onto the altar to see what would happen - what they would do to get out of that situation.
The Warlord, a new PC - replacing the Cleric - said that he had created a small sympathetic doll that would take the curse instead of him. Arcana roll (Hard) = success! He undergoes a ritual - soaked in the blood of a sacrificed pig - but suffers no ill effect.
The Warlock is next. He says he already believes in the power of Orcus, and he didn't need the blood ritual. "Good, then," Kalarel responds, "you can have the fire!" Bones burning with a sickly green flame scorched his flesh.
Yes, this was a failure.
Then we turn to the Fighter. Who, remember, had broken his bonds. He's thrown on the altar. "You are the most stubborn," Kalarel says. "You will taste the knife of Orcus!" He draws a knife, preparing to plunge it into the Fighter's chest.
The Warlord responds with a Scorching Burst right on the altar. "The holy flames of Orcus!" he says. "He is already blessed!"
Yeah. Kalarel is not buying it either. "Betrayal!" he shouts. The Warlord runs.
Now the Fighter makes his move. He flips out and goes all bad ass. He crushes the throat of the vampire spawn next to him. He punches the underpriest in the face and breaks his nose. He kicks Kalarel in the gut and winds him.
We're at 7 successes and 2 failures. What's the Warlock going to do?
It's down to the Warlock's roll; success or failure, it's going to be resolved here. Will they be swarmed by the Kalarel and his bitches, or will they break out?
The Warlock makes his move. He calls a flaming claw from Hell to grab the underpriest and throw him down the well. The underpriest tries to dodge, then to wiggle his way free, but he's stuck. He gets tossed down the well. All they can hear is a loud splash.
The PCs decide to beat feet and get out of there before Kalarel can rally his troops.[/sblock]
This is what I think you do:
1. Get a good juicy conflict going. If the PCs don't care about the outcome or the NPCs don't care about the outcome, don't roll.
2. Play out the NPCs. Have them take steps to accomplish their goal. Since this is a new sub-system, players are going to need the occasional prod: "The (bad guy) does (this). Are you just going to take it?" The players need to make all the rolls, so mess with them if they don't.
(Playing out the NPCs includes stuff like: "The river rages and smashes your boat with malevolent force, tipping it over" or "The hot sun shows no remorse. It beats down on your thirst-ravaged bodies and you collapse on the ground, exhausted." At which point you might have to prod: "Unless you do something about it.")
3. Roll the dice to resolve each each action. Good, general results to use with a failure are penalties/increased DCs to future rolls, blocking out skill use ("You've pissed him off, Diplomacy won't work"), and draining Healing Surges. The opposite are good for success (bonuses/reduced DCs, enablind skill checks, and regaining Healing Surges).
4. Stop rolling when the conflict comes to an end, and make sure that this particular conflict ends when the number of successes or failures have been reached. It could spawn another skill challenge right after the first; that's good.