This started as a comment in a blog post by DM David which went a bit long. David was discussing how to encourage “role-playing”, by which he means social interactions with NPCs. I personally think you’re role-playing any time you’re making in-character decisions, but here is my advice if you want to encourage social interactions.
Basically, if you want players to talk to your NPCs, give them interesting NPCs to talk to. That does not mean caricatures or over the top personalities. It means making NPCs who are like real people with real wants and needs and fears.
I’m not a big fan of adopting funny voices or peculiar mannerisms. I find they distract the players and turn them off the characters. I just keep the character’s basic personality and motivations firmly in mind and just _talk_, sometimes in first person and sometimes in third, and describe reactions and facial expressions.
It works beautifully. I remember a session where a PC, via the player, was arguing with his mother, run by me. It was anguished and poigniant and perfect, and would not have been improved in the slightest by me putting on a falsetto and sounding like a Monty Python granny.
You can also reveal a lot about characters by describing their choices and actions. Just keep who these people are in mind, make the choices they would make, and tell the players what the NPCs are doing from time to time. Role-playing is not just the talky-talky bits, it is the choices and actions you are always taking.
For example, I once ran a campaign for a party that included 3 NPCs who were involved in a love triangle; two were involved with each other and one was left out and jealous. I didn’t plan it, it just seemed like what would happen in the circumstances.
The involved couple wasn’t broadcasting it, so I didn’t do anything overt, I just mentioned general demeanour and who was sitting next to whom and what actions they took. Eventually someone noticed that jealous dude would never heal his rival during combat. The PCs confronted him, and the whole thing came pouring out, culminating in a discussion as to whether the couple were too distracted with each other to be on watch together. It was a great payoff for just making in-character decisions, and a setup that involved no verbal interaction whatsoever.
But the point is, the players gave a crap about those NPCs because I ran them like people. Frail, fallible people. If you can develop real personalities, and keep them firmly in mind, the rest will follow.