Ridley's Cohort said:
Third of all, if you train your players to chant "Sense Motive! Sense Motive! Sense Motive!" during every important seeming NPC interaction, you have only yourself to blame if the game bogs down.
I don't bother to roll and just say "You sense nothing special". I do this with Search rolls out the ying yang as well.
My players are smart enough and mature enough to not become "I want to roll xyz skill" monkeys (now that I am back to being DM as of last Sunday).
The other aspect of this, especially with Bluff / Sense Motive, is that it detracts from good roleplaying (and really shouldn't be skills in the game anyway). Players should be able to come up with their own ideas, their own suspicions, and their own ways of handling problems without the DM making rolls and handing information to them.
Ridley's Cohort said:
Fourth of all, by the RAW, if the NPC is using the Bluff skill, then the PC gets the Sense Motive roll. Simple as that.
Not necessarily.
If the Bluff DC is so high that the PC cannot overcome the DC, then there is no reason to roll Sense Motive. A roll of 20 is not automatic success for skills.
Also, it is a mistake to use Bluff / Sense Motive for every single conversation as some form of constant lie detector. Virtually everyone prevaricates at some point when they talk, but nobody is really able to know that unless the person is making a semi-outrageous statement, or the person is nervous, or the conversation has gone on for a lengthy period of time and someone has an opportunity to present flaws in "his little white lies" (which should be picked up via roleplaying, not via dice rolls). Even when someone has unusual body language, it might be due to him lying, or it might be because he is late for an appointment.
And in the case of nervousness, a person could appear to be "hiding something" or even lying when he is actually telling the truth (which is not reflected in the Bluff / Sense Motive skills).
So, you shouldn't rely on Bluff / Sense Motive unless the information borders on the outrageous or the suspicious, or the information is critical to the story line.
For example, your Fighter is walking down the road and needs directions and says "I ask the first guy I come across how to get to the tavern". The particular NPC he meets dislikes warrior types and likes playing practical jokes, so he says "Head east down this road" when it should be west.
I don't really consider this a bluff per se. The Fighter is not really expecting the stranger NPC to lie to him, the conversation is short, and there isn't much of an opportunity to discern that this guy might be lying. If the player asks for a Sense Motive, I will give him the roll (with a +5 for being suspicious). But at best, I consider this a Take 10 Bluff where the Fighter's Take 10 Sense Motive with a -5 for believability and another -5 for extremely short conversation is not going to pick up on it. The situation is not critical, the story is not tense at that point, the player of the Fighter is not indicating that he is suspicious of strangers.
Also, nobody is going to tell the truth, the whole truth, and nothing but the truth in every conversation unless it is with a close friend or acquaintance. Someone might tell the truth, but they will often be holding stuff back. That means that "according to RAW", you should be rolling Bluff / Sense Motives all of the time and almost half of the time getting "he appears to be hiding something". That's just silly.
It's much better to just use this when the situation is tense, the players are suspicious, or it is critical to the storyline and blow off using it for every conversation where someone might want to not tell everything they know, hide something or tell a little white lie.
This is like Hiding. If you have adequate concealment, Hiding should be extremely easy and really tough to notice. If your lie meshes with the conversations and sounds extremely believable, Bluff should be extremely easy and really tough to discern.
But, following RAW for dice rolling concerning roleplaying conversations is kind of silly unless it is important or unless your players want it to be important. The entire point of roleplaying is so that people can figure stuff out for themselves based on what is presented and have fun doing it. Overuse of Bluff and Sense Motive is the antithesis of good conversational roleplaying. IMO.