Priya, I think it's mostly learned by breaking them, but watching first helps a lot. In Sweden I spent my first week just observing at the bus stop before I tried anything: where people stand, whether they queue, who gets on first, whether they talk. Everyone stood in a loose line with a surprising amount of personal space, and nobody spoke to anyone. That told me more than any guide.
A few things I've learned since, by watching or by getting it wrong:
- if there's an empty double seat, take it. Sitting next to a stranger when there are free seats elsewhere earned me a look that was very polite and very clear
- the quiet carriage on regional trains really is quiet. Phone calls happen in the space between carriages
- let people off before getting on, even when it's raining and you're getting wet
- on the escalator, stand on the right, always
My kids learned all of this in about three days by copying other kids. I needed a month.