The session I GMed last night was my group's first truly heavy brush with RP encounters (Act 2 of Long Arm of the Hutt... if you've played that then you know what I'm talking about), and I can't help feeling like things could have gone smoother.

In this situation, there are a lot of people and a lot of half-truths and lies being thrown about. Let me break down my areas of concern with how things went:

1) When someone tells a lie, they roll their Deceit Skill versus the target's Discipline Skill. Is this for every lie or just when the lie is meant to cause the target to take an action they otherwise would not have? For example, does an art thief casually introducing himself as a museum curator trigger this roll? Or would the roll be reserved for cases where you're trying to manipulate the target into taking an immediate action they wouldn't otherwise, as in "Run! There's a platoon of stormtroopers coming this way!" When in reality it's just a civilian convoy in the distance.

2) Does this change when the target is a PC? In last night's game I had them roll whenever they tried to deceive an NPC, but for the most part did not make a roll for the NPCs to deceive them as just asking for the check is a sure sign that there is a lie being told. And they're a good group who mostly avoids metagaming, but it'd still be annoying to know your character is getting taken for a ride but unable to do anything about it.

3) What about people present, but are not the "target" of the Decive check? For example, last night one player was engaged in a lengthy conversation with an NPC. I had him roll the Deceive Check and mostly ignored the other players as they were not active participants in the conversation. Five minutes later another player, whose character was standing next to the one doing the talking, asked if his character thought the NPC was being honest. What do I do there? Roll another check? Try to remember the total previously rolled for the NPC's dice and make that a difficulty number for the 2nd player's new Discipline Check? Tell him to make a Perception Check to make sure he heard the conversation in the first place? Or to see if he saw any nervous ticks or other signs that the person may not be honest instead of Discipline?

4) We come from systems that used "Sense Motive" or "Insight" checks. That seems much easier to me. We role-play and if a player is suspicious they may roll their Sense Motive versus a difficulty rating known only to me. Then I tell them "You think he's telling the truth" or "You don't think he's telling the truth." If I tell them "You think he's telling the truth" the player doesn't know if that's because the person really is honest or they failed the roll... because they don't know what the difficulty number to beat was in the first place. That system also addresses the above situation of someone present for the conversation but not the target of the Deceive Check. So, is there a "Sense Motive" or "Insight" type skill in the FFG system? Using Discipline just doesn't feel right for this purpose...

Any advice is appreciated.

TL;DR I've made a mess of social encounters with my players.

Rolls of social skills should not be done for each instances of interaction, but only for the sum. Several lies told in succession would still only be one Deception roll, just as several shots are included in a single Ranged (Light) attack. Rolls should likewise only be made when there is some kind of intended outcome. Meaningless lies that are unlikely to matter and won't change the target characters' intentions don't need to be rolled.

As for the PCs being lied to, remember to roll only once for the entire conversation. There might be some truth in there too, so knowing what's true and what's false depends on the outcome, but overall the roll represents if the acting character can sway the actions/reactions of the target not whether or not he/she is believed. Threat and Despair can create some incorrect assumptions too.

Bystanders can, at best, add a Boost die to the main participant for their extra skepticism. Don't add additional checks.

There is no Sense Motive/Insight. You don't have a lie detector in this game. You instead have the ability (Discipline or sometimes Cool) to not be swayed by what they want you to do.

1) it depends on your GM style. In this system I try not to have so many rolls so in a social encounter spanning a long conversation I would make a general overview roll to see if the players believe his overall attitude, meaning is he truthful or lying in general (in some cases I wouldn't even tell them what the roll is for I'd just ask for a disciple or cool roll and note it for later). Then I would use that roll to add setback or boost dice when the players decide to challenge something specific he says.

2) I allow the players to make almost all rolls except combat against them and interactions with Nemesis NPCs. So, yes I would make the players make an opposed roll vs the NPCs Disciple. If you are concerned with them knowing by a roll you can make the opposed roll in secret and then narrate the result. When I have NPCs interacting with PCs I generally don't roll at all unless the player calls for it. There is no reason to believe someone is lying to you unless you have a reason, for me the reason is the player asking me "I don't trust this guy, is he lying to me?" Then I'd say ok make a roll then narrate the result. A lot of times the NPC isn't lying and the player calls for a roll anyway so by letting them initiate the roll they never know for sure.

3) see #2.. Again, I never have a roll about deceit unless some player asks for it. Even a player standing nearby listening can ask for the roll if it makes sense they could be hearing or involved.

4) Disciple is basically sense motive in this usage of the skill. You might want to listen to the skill monkey podcast on Disciple. However, we use it just like sense motive which in our play sessions is an active skill use not passive. The way we think about it is people lie to you all day long, everyday that you talk to in real life maybe small things maybe big things, but unless you have reason to really question it you accept all the "white lies" as truth.