Jesse Coombs when a PC asks something to an NPC it’s not always a conflict, it can just be chit chat or assessing their interest. So there is a phase where you just talk between PC and NPC and assess the situation: that’s probably the moment that the TN should pop out. “the NPC is not interested in your idea, if you want to convince him it will be hard, let’s say TN 18”. At that point the PC has not YET engaged in a real “social conflict” to convince the other party, so he can back off and never roll.

Even if the PC directly told me “I’m trying to convince him of this” I would first tell him “he seems very reluctant on that idea”.

This is my style of GMing and the one I’ve put in my system too. I don’t say is the best or whatever, just how I evaluate things.

Also, for me a conflict/roll arises ONLY if its result is meaningful both if the roll have success or fails. So if the only reaction from the NPC would be “no, I’m not convinced”, I wouldn’t even bother rolling: either the PC accepts the NO, or he convinces me that he has plenty skills/Traits (and maybe spends a KA point) to convince him, or if he really wants to roll…well at that point he knows that if he fails something BAD will happen.
Such as the NPC becoming upset at his insistence and putting him in prison.
Thus I try to convey the idea of the difficulty of rolling both through the mechanics of the game and what I say, way before the player rolls.

A different example follows (next post)