Diplomacy represents the ability to get others to peaceably come to an agreement, to convince others that you believe something to be true, and to get others to be willing to make a deal.
What can you do with this skill?
Changing attitudes: Too much, and none of it good. Everyone knows about the problems with Diplomacy. Mohr covered them here, and plenty of other people have done the same. I actually don’t have much to say here, because the brilliant Justin Alexander has already done the work, building off of the also good work done by Rich Burlew.
So, go here and read this: Advanced Rules: Diplomacy. The series leading up to that final article is also required reading, if you want a good understanding of the problems of Diplomacy.
In essence, you should use Diplomacy to make deals, get someone to listen to you long enough to make a deal, or convince people of something you believe. Attitudes towards diplomats are NOT adjusted by Diplomacy; rather, those pre-existing attitudes affect the chance of a successful Diplomacy check, as they should. These are pretty solid rules, but they were written for 3.0/3.5, and thus, require some nitpicky changes (these are also required because of the changes I’m proposing in these here articles, natch).
First, there are no synergy bonuses, which were thoughtfully removed from Pathfinder.
Second, the time it takes to make a deal should not be set in stone. While one minute is a reasonable amount of time to set as a standard, the art of making deals and influencing people cannot be easily quantified. Sometimes it takes weeks or years to make a deal (like, multinational summits with heads of state), and sometimes, it’s as simple as trading your grilled cheese for someone else’s hot dog (which hardly takes a minute, and is not exactly what I’d consider finessing the art). The DM should consider the complexity of the deal in all its glory; and certainly making complicated deals in a standard action (6 seconds!) should not be allowed no matter what the penalty. It takes time to present a case in a meaningful way. So use one minute as a guideline, not a set in stone rule.
Third, people can lie. Someone may say they accept a deal when they don’t. This moves into a tricky area; you don’t want players feeling cheated by liars every time they attempt Diplomacy checks. If they pass the check, the deal is accepted. But shouldn’t the DM roll Diplomacy checks? What if the DM rolls the check, the character fails, but the target of the check decides to lie and set up the character’s downfall? There are some slippery slopes in here when dealing with antagonistic characters. Letting the players roll the dice removes the likelihood of this happening, and gives the characters more information than they should have, but also speeds up the game and gives the immediate feedback as to what just happened. As always, the DM should use good judgment and mix it up occasionally just to keep the jackals on their toes.
A note on magic items and Diplomacy: you know how you can make custom magic items that grant Competence bonuses?
Don’t be a sucker DM and let players make one with a bonus higher than +10 (in regards to any social skill). You’re just begging for it if you do. Actually, +10 is a good cap for non-epic items that enhance skill, as a rule of thumb. I’d strongly consider limiting the bonus to +5 for social skills, but +10 should work.
Final Analysis: In a role-playing game, social skills are often difficult to model. If you rely on player skill then let’s hope you have some diplomatic players willing to engage. If you rely on the dice and some skill ranks, then you risk letting players run roughshod over NPCs while saying and doing the most heinous things. RB and JA have done a good job in making Diplomacy so much better that I can’t help but admire what they’ve done with the thing. I generally fall on the side of making player skill always count for something; but each DM is different. When roleplaying a character, however, it’s a drag to envision a silver-tongued bard but be unable to play such a role because in real life you are a painfully shy sufferer of Tourette’s Syndrome. The game lets us play things that we are not, and so we need a way to quantify such things. So use Diplomacy, but temper its use with reason. This isn’t a Rule Zero fallacy; I’m not saying to ignore things that make no sense, rather, take into consideration the circumstances of the game and modify accordingly.
Disable Device represents a character’s understanding of simple mechanical devices, traps, and locks.
What can you do with this skill?
Fuck around with traps and stuff: So Find/Remove Traps and Open Lock got married, and had a baby, and it inherited some features from both parents. This skill is used to fiddle around with all sorts of mechanical devices, but which ones? What defines a simple mechanical device? A catapult? A trebuchet? And what about Rube Goldberg levels of complexity? The skill is clearly intended to deal with traps, but one could hardly call a Goldberg device simple. And why can someone with Knowledge (Engineering) not do many of these same things?
The name of the skill is rather problematic, in that it fails to capture the true meaning, purpose, and essence of what the skill is intended to do. Tinkering? Technicianing?
What the skill is really intended to do is be a catchall for all of the things an adventuring ne’er-do-well will have to do in the course of looting some location that does not want to be looted. It’s a combination of low-level field engineering with sabotage thrown into the mix. It works as written for the most part; I’ve never had a situation where I felt the skill wasn’t living up to its purpose. We’re stuck with that name.
As for magic traps, I don’t see why Rogues should be the only ones who can disarm them. What, the Wizard can’t deal with magic now? Rogues should be the best at trapfinding, but it’s not their exclusive purview. I’ll address this in a later piece, but in general, I’d let anyone with Disable Device do the things it’s good for without restriction.
Open Locks: The system is balanced around the assumption that you’ll take 20. Do this as often as possible; it’s how locks are meant to be picked (not that locks are meant to be picked…). You will rarely be in a situation where time is of the essence when picking a lock; it’s either a corner case of extreme rarity or you’ve already screwed up somewhere. Picking locks is an activity that requires planning, so do so.
Final Analysis: Disable Device works. I think of it as representing a Howard Wolowitz knowledge of engineering, vs. the Sheldon Cooper knowledge that is the actual Knowledge(Engineering). Wacky, right? But go crazy with this one, it does the job.