It's good to know all of the different elements to writing a character, beyond accents or slang which can come across as being heavy-handed if not handled carefully. I'll try to pay more attention to the way my co-workers speak; it would work with customers too, but my interactions aren't nearly as lengthy and numerous, and I think there'd be plenty to gain from the people I work with on a regular basis. But sometimes there are very eccentric customers, or one can cautiously generalize across customers, which I'm sure would work fine for minor characters at the least. I'll also start analyzing some interviews! I have noticed that actors and other celebrities often have very unique personalities, and it's a lot more exaggerated. Thanks for reminding me! You're right that minor tweaks to how a character speaks (paired with the corresponding actions) with certain characters can reveal a lot about relationships, and the individual characters involved. It's something that one would probably only have to do a little bit in sprinkles to get across the point for the reader. It could be argued that somebody who doesn't do this^ has a very strong "take-it-or-leave-it" personality, and/or likely a position of great authority. I'd also like to get to a point where the dialogue also reflects changes in the character, growth or otherwise. For example, a character who initially is pretty positive, but that dwindles and eventually disappears at the end of their arc. Or similarly, a character who seems in high-spirits but in private is lost, which can be pretty typical of depression. Maybe I'm thinking about it too much, but you seem to hint at an implicit distinction, that characters don't just have motives relative to the plot but also motives that pertain to their own personalities. For example, "liking to be (and/or seem) knowledgeable" would have broader implications than just being limited to those that are oriented directly toward the plot. Keeping this in mind, I assume, would help in part to ensure that the characters aren't there to just deliver plot, as you say.