There are certain universal laws of conduct that apply the world over, such as do not kill, do not run red lights, do not randomly scream “fire” or “bomb” in a public place, do not try on underwear at a clothing store, do not smile when taking a passport photo, do not fart in a bathtub (in a Jacuzzi is OK, though), do not clip your toenails at a restaurant, and so on and so forth.
And there are various unspoken rules of decorum that vary from place to place, and are specific to each given locale or culture. This is particularly evident to a foreigner marooned abroad like moi, as I have to traverse the minefield of Malaysian etiquette on a daily basis.