Writing "classic" scene types

Writing a "common" or "classic" scene can be tricky. This is the kind of scene you can expect your readers to have seen or read dozens of times before. But maybe more importantly, it's probably a type of scene that you have read dozens of times before. If you're not careful, you can write the stereotype of the scene type instead of simply achieving the purpose of that scene type.

Here's Terry Pratchett, in Feet of Clay, writing a classic scene type in a way that works well:

"... Why you wanna know about clay?"

"Can't you tell where it came from?"

Igneous took the tiny piece, sniffed it, and rolled it between his fingers.

"Dis is crank," he said, a lot happier now that the conversation was veering away from more personal concerns. "Dat's like... crappy clay, jus' good enough for dem lady potters wi' dangly earrings wot make coffee mugs wot you can't lift wid both hands." He rolled it again. "Also, it got a lotta grog in it. Dat's bitsa old pots, all smashed up real small. Makes it stronger. Any potter got loadsa stuff like dis." He rubbed it again. "Dis has been sorta heated up but it ain't prop'ly baked."

Context: Angua, werewolf cop (officer of the Night Watch) is visiting Igneous, a troll who works as a fence and a supplier-of-things in Ankh-Mopork's criminal underworld. (Or, as Terry describes him, "a wall, which was the same as a fence only a lot harder and tougher to beat.") The Night Watch have three murders on their hands and at each scene they've found bits of white clay – what Angua is asking about.

(Aside: I feel like I've read the phrase 'beating the fences' before for an idea closely related to this scene. From what I recall it roughly meant: Putting pressure on low-level criminals to give up information relevant to an investigation. Unfortunately I don't get any results when I search for this. Igneous isn't quite low-level, and there isn't any pressure, but there is an investigation.)

This is a classic police procedural scene type, but the way Terry tells it, it still feels interesting. You can feel the tension in this scene, and the writing works with this to paint a charming picture of Igneous the troll, his warehouse, and his relationship with the Watch from Angua's perspective.

(Actually, this scene feels sort of funny. It's not quite exactly a "beating the fences" scene, because there's no pressure on Igneous nor suspicion in his general direction. It's more like an "talking to the lab techs" scene. That seems sort of relevant. Some of the tension comes from their conflicting interests as police vs. criminals. But some of the upfront tension comes from Igneous thinking he's in trouble – more like "beating the fences" – while Angua is treating this more like "talking to the lab techs.")