I'm one of the younger generation, but my parents still managed to teach me common courtesy. You don't need corporal punishment, you just need to appeal to the tendancies of the generation.
For example; being raised in a relatively high-speed society (mobile phones, email, fast food, microwave meals), I've developed an inner necessity for getting things done the fastest way possible. I dislike unnecessary waiting, as I could better spend that time doing other things.
So to curb my fast talking, low politeness attitude, my mother would constantly correct me, and make me repeat what she said. If I said "yeah," she'd say "yes," and I'd have to say "yes." Same for please, thank you, you're welcome, ma'am, sir, excuse me, etc. It got to the point, where it was more expedient for me to be polite, so I've become polite out of reflex.
Verbal conditioning. It works.
Note: I have found to the contrary, that if you are too polite in retail, people become suspicious. I actually had to curb my polite tendancies, or customers would give me the brush-off, thinking I was just trying to sweet talk them into a sale.
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