Between the Monster Manual, Volo’s Guide to Monsters and various third party products NPCs that participate in combat are easy to find or tweak to your needs. But DnD is about more than combat. Social scenes and exploration scenes are not just important. They are a foundation of the game.
Whether it’s a simple quest giver in bar, a noble man’s guard you need to get information from or any other non-violent denizen of the world many NPC templates give you more game data than you need.
What I need when DMing a social encounter is a visual description, a modest amount of psychological info and a couple skills that might come up for dice rolling. I also want a few of these ready because my PCs are notorious for drifting off track. If I prep two characters they’ll want to talk to the third guy, the fourth gal, maybe that drunk under the table and that one dude they passed on the street a few minutes ago.
Whipping that up in 10 seconds is hard. Instead I prep a dozen or so NPCs that they may encounter. Each only needs tiny updates if they aren’t used that session. I jot these down on an index card because table space is at a premium (I also can create them on a spread sheet for latter reference or digital fun).
I present these to myself in two columns (visual and behavioral)
|Two good attributes||Race, Class if applicable|
|Zero to Two bad attributes||Role in society (job), 2 skills|
|Armor/Clothing||Country of origin|
|Single Weapon||Goal in life|
This basic snapshot of the individual can inspire role-play and allows room to for ad hoc play. If one of the PCs tries to take advantage of a weakness I grant advantage. If they help towards a goal I usually grant success.
If an NPC lives a lifestyle (from PHB) that is beyond the expectation for a societal role it probably means that there are deeper levels for the character. If they are a noble and living in poverty that too is an indication of something beyond the norm.
Goals and weaknesses can be grabbed from the PHB and SCAG’s backgrounds, or you can invent your own. The point isn’t to be as data reliant, but instead let your imagination and table inspiration take over. Be just prepared enough to take advantage of the multitude of voices informing you during your game.
Now, when my players wander off script in a town, I have a dozen of these ready. When one gets used I can add it to the folder in case they want to go back and chat again. I then make a new character.
Having a many of these prepped helps because it ensures I use naming conventions that are consistent to the region of origin and the land where they meet the heroes. On-the-fly NPC creation is unlikely to have that consistency.