Setting DCs
Source GM Core pg. 211
When setting DCs, it's often good to start with a noncombat level or “social level” for the NPC and set their DCs accordingly. Use the DC adjustments just like you normally would. A good starting place is setting the NPC's Will modifier, then taking that DC and adjusting it for skills that are more or less likely to work.
For instance, for a 3rd-level challenge, you might give an NPC a +12 Will modifier and use 22 as the base DC. You might say that's the DC for Diplomacy but then determine that the NPC is difficult to intimidate, and so you apply the hard DC adjustment to make the Intimidation DC 24.
Returning to the example above, maybe you also determine that the hacker NPC loves talking about vidgames, resulting in an incredibly easy DC adjustment to get DC 12 for Vidgame Lore. To represent her judgmental nature, you might decide the hacker isn't easily impressed by others' technical prowess and make the check to show off with Computers challenging, applying the hard DC adjustment to make the Computers DC 24.
For instance, for a 3rd-level challenge, you might give an NPC a +12 Will modifier and use 22 as the base DC. You might say that's the DC for Diplomacy but then determine that the NPC is difficult to intimidate, and so you apply the hard DC adjustment to make the Intimidation DC 24.
Returning to the example above, maybe you also determine that the hacker NPC loves talking about vidgames, resulting in an incredibly easy DC adjustment to get DC 12 for Vidgame Lore. To represent her judgmental nature, you might decide the hacker isn't easily impressed by others' technical prowess and make the check to show off with Computers challenging, applying the hard DC adjustment to make the Computers DC 24.