I’d consider it fair use to summarize one of the social skill challenges presented in the DMG; if you consider it illegal, feel free to ignore or remove this part of my comment.

Interrogation (Complexity 1 challenge; 4 successes before 3 failures)
Primary skills:
Bluff (moderate DCs): used to trick a prisoner into revealing something. Failing at Bluff eliminates its use for the rest of the challenge and increases other DCs to hard.
Diplomacy (moderate DCs): used to bargain with the NPC. If you earn 3 or more successes at this, you must hold up your end of the bargain (the book is unclear how this is enforced).
Intimidate (moderate DCs): used to threaten the NPC. Failing at Intimidate eliminates its use for the rest of the challenge and increases other DCs to hard.

Success at this challenge would mean that the prisoner provides the desired information; failure would indicate false information or silence.

Wizards has released a free preview of an interesting social skill challenge from the DMG2, no Insider subscription required:
http://www.wizards.com/default.asp?x=dnd/4ex/20090831

Two interesting social skill challenges online:
http://at-will.omnivangelist.net/2008/11/skill-challenges-3-demon-dialogue/
http://dungeonsmaster.com/2009/02/skill-challenge-information-gamble/

And a long list of skill challenges, many of them social:
http://www.critical-hits.com/features/skill-challenges/

All this is with the caveat that I have not yet gotten a grasp on skill challenges and how they are best used… or even if they are useful. They certainly seem useful, especially if you tend toward several connected low-complexity skill challenges, but I have yet to be satisfied with a skill challenge I’ve actually run in-game.

The most important thing that I’ve found about skill challenges is that the mechanics must take a back seat to the roleplaying. Skill challenges do not take the place of roleplayed encounters; they provide a way to keep score mechanically. Essentially, the GM proceeds with the interaction as if it was being roleplayed normally, and uses the skill challenge rules to decide when the conflict has reached its conclusion and what conclusion has been reached.

This is a spectacular discussion of skill challenges (both social and non): http://www.critical-hits.com/features/skill-challenges/

I’m going to toot my own horn here and offer up something from my blog. We banged out (but never tested) a system that treats social conflict like combat. It is in two posts:

http://mediocretales.com/?p=400
http://mediocretales.com/?p=433

I should note that I gave the scenario 4 out of 10, as we were required to rate them. In any situation but the convention, I would certainly have let a plausible idea save the characters, but even then, it would have been awfully challenging to come up with such an idea, however, due to the situation the scenario creates.

So; I don’t think it is necessary to tell that everyone is going to die, but I do think it would be generally a smart thing to communicate.

I find no real problem in an scenario where you have elements that are impossible to influence, as long as they’re made clear to me. Basically, there are certain established assumptions about what role-playing is and what to expect that are different for everyone. To avoid unnecessary frustration, it should be made very clear that those expectations do not hold water.

Granted, it is not possible to shield oneself (and the group) from every possible expectation. I would say, however, that the idea that the characters have some saying on the fact that their characters live or die at the end of the story… is pretty widespread.

Fred.

Is feel something that only happens after playing?

You can already get a ‘feel’ from TV programs. The author seems to have deteremined about 90 to 95% of the feel with this, while the players add a little colour at around 5%.