I love sushi, pretty sure you love it too, but the etiquette, do you have the etiquette? There is some you know, truly. I can't say I was aware of all of this before I read it but this guy has a pile of it. Have a read it's pretty interesting.
It's not your fault. The finer points of sushi etiquette are largely unknown outside Japan.
The absolute biggest no-no for nigiri is dipping it rice-first into the soy sauce. That's because the rice has already been perfumed with a mixture of rice wine vinegar, sugar, salt, a cooking wine called mirin and kombu or seaweed. The chef wants you to be able to taste all that. The sushi chef has also packed the rice by hand so that it falls apart when it hits your mouth. If you dunk it in soy, some stays behind in the dish and makes a soupy mess.
But never, ever eat pickled ginger on top of your sushi. It's a palate cleanser to be eaten in between different kinds of fish.