Using NPC actions

By Krusader, in WFRP Gamemasters

This question may be better off in the rules section, if that's the case I apologise.

My question is, how do GM's go about using NPC actions, primarily in Social interactions.

For example, if I have an NPC who I want to tell a bold face lie, should I make that an opposed check? Or would I be better served to let the PC's believe it unless they make an intuition check if they decide they want to? I am tempted to go with the second option as I could then have another NPC contradict the first one, there by exposing the possibilty that one of them is lying.

Oh and one other quick question, The Merchant from A Day Late, do I roll for his actions in the open? Or do I do them in private? How do other people do it?

Just after some other people's experiences and opinions on what works.

Thanks
Krusader

I try to have PCs use their skills and have them rolling the dice anytime that is possible. If an NPC is trying to influence a player let them roll Discipline (Willpower) for example and set the difficulty by opposed check (remember, NPC expertise gives misfortune die).