4. Additional details

Fill in the rest of an NPC's details only as they become important and relevant to the story or to how you portray them.

If you're making the NPC up on the fly, you likely won't have time or the mental bandwidth to do these intentionally. It's common to just portray new NPCs naturally and instinctively, based on what you've already established. You can then go back after the session and take notes about how you portrayed them, and/or flesh out some of the missing details.

If you're prepping an NPC in advance, think about the following areas and make some decisions about them. But remember: prep only what's useful and valuable to you.