One thing I miss from older editions of D&D is a table that gives some guidance to a DM on how a random NPC (or mob of NPCs) react to PCs when roleplaying isn’t applicable (for example the players are not in the mood, or its a very minor thing like interaction with a guard). I stole this from the Warhammer 40 RPG. but it’s very similar to interaction tables from previous editions. Here is something I have stuck to my DM’s Shield for reference.
INTERACTIONS
| DISPOSITIONS BY SKILL | |||||
| Difficulty | DC | Persuasion | Deception | Intimidate | Other Cha |
| Easy | 5 | Infatuated | Gullible | Terrified | Fanatical |
| Routine | 10 | Affectionate | Trusting | Frightened | Devoted |
| Ordinary | 15 | Favourable | Accepting | Startled | Loyal |
| Challenging | 20 | Indifferent | Indifferent | Indifferent | Indifferent |
| Difficult | 25 | Disdainful | Suspicious | Brave | Resentful |
| Hard | 30 | Contemptful | Sceptical | Courageous | Disloyal |
| Very Hard | 35 | Disgusted | Disbelieving | Foolhardy | Mutinous |
First, determine the disposition of the NPC to the PC. Crossreference that with the skill the PC is using to change the NPCs disposition. That is the minimum DC required to get that level of disposition – which may not be what the PC wants. For each degree of success – where a degree of success is each 5 points above the minimum DC on a d20 check – the PC moves the NPCs positively.
For example, an NPC has a disposition of indifferent. The PC makes a DC 20 Persuasion check and rolls a modified 25. The NPCs disposition is now favourable.
Generally, a target must at least be Indifferent to do as requested, and then the target will only do what the player wants 50% of the time if left to his own devices. Each step above Indifferent indicates that the target is 10% more likely to do as requested. Under supervision, the base chance increases by 20%.