Bluffing - a skill based on your PC's Charisma - seems to be straigtforward: your PC knows how to BS an NPC. Not quite so simple, Bluff is actually three useful things.
- How to tell a lie
- Feinting in combat
- Passing secret messages
All PCs can try to do the things listed but with the Bluff skill a PC can actually succeed. Ok now the mechanics:
The check is against the Sense Motive skill of the one being hoodwinked.
The modifier for lying depends on actual lie. There is a table provided. An impossible or impossibly stupid lie gets a -20 modifier, a good lie gets +0. If the recipient is inclined to believe you you get a +5. This is, as you guesed GM discretion
Takes one round.
A successful feint means you have put your opponent in a physical disadvantage in a fight shown by said opponent not being able to use Dexterity modifiers to her AC.
Now lets talk about defending against your Bluff(Feint) on your opponent's side:
If your opponent has the Sense Motive skill: DC = 10 + Sense Motive Bonus.
No Sense Motive: DC = 10 + Base Attacck Bonus + Wisdom modifier
Opponents with Sense Motive role for both DCs and use the higher one.
Feinting is a standard action.
Done by using innuendo. This is really situational but you might find yourself in this position in an adventure. The DC is 15 for simple messages and 20 for complex one. 20 on complex essentially means keep your messages simple. Doing a 10 or below for the former and a 15 or below on the later means that anyone with a - you guessed it - Sense Motive skill has a chance of deciphering your so-called secret message.
Secret messaging takes twice as long as normal messaging.
Not only am I beginning to appreciate Bluff, I'm beginning to appreciate Sense Motive. Both of these skills would be great for the plots and counterplots in royal courts.
Ok one take away is that Bluff, by supporting Feint, can become a martial skill. An oh so handy detail when you're stealthy rogue gets discovered and has to do an unpalatable bit of face-to-face fighting.
Another take away is that not all PCs can pull off the fine art of bullshitting or feinting or passing on secret messages - the Bluff skill is needed to increase the chance of success.