A skill challenge is a group Skill Test. The GM will tell the players what they are facing. The GM will then set a Skill Challenge DC. The players will determine how best to thwart what they are facing, and lay the plan out with the GM. The players and GMs will come up with 1 Skill Test for each player.
Each player than rolls their Skill Test. The GM will tally the results. If the majority of all players currently playing meet or beat the Skill Challenge DC, it is considered successful, and the players succeed. If the majority fail, the skill challenge is a failure. If there is an even number of players, the GM should determine first if a tie goes to a success or failure, and tell the players of this information before they roll. If a GM is unsure, or doesn’t wish to decide, the default rule is that one-half of the players succeeding is considered a success.
Many journey and dungeon procedure rules use Skill Challenges, but you may find additional uses for them as you play. For example, if a group of 5 adventurers are attempting to sneak passed a guard, a Skill Challenge would be appropriate. It’s true the warrior and priest in chain mail armor would likely ruin a skill test for stealth if individual Skill Tests were rolled, but a group skill test could represent collaboration that allows the players to still potentially be successful at using stealth.
The group is attempting to look for information about their next treasure hunt, and hit up a local bar for information. The GM decides to set a Skill Challenge with a DC of 10 to successfully gather information. Since it is a party of 4 players, he also tells them that a tie will be considered a success.
Astril decides to put her wisdom to use, and simply attempts to eaves drop on some conversations.
Brynjolf decides to attempt to use his strength, and offers the bar “silver or information” if the patrons can beat him in a contest of strength.
Cerrig decides to put on the charm, and use his charisma to simply talk information out of folks.
Derrian decides to put his intelligence to work, and tells the GM he is going to take all the rumors the others come back with, and see if he can put all the clues together.
The GM likes all responses and has them all roll. Astril, Cerrig, and Derrian pass, but Brynjolf fails. Still, a majority pass, so the GM will give some information to the party.