In Japan, sushi is everywhere – in railway stations, on conveyor belts, in supermarkets and even vending machines. But great sushi happens only in the hands of a great sushi chef (known as an itamae), with just seconds passing between him forming it by hand, and you eating it by hand. It's this direct connection that turns the simple creation of vinegared rice and raw fish into theatre, art and religion rolled into one.
The thing is, if you go and put ginger on top of your sushi and wash it down with Coke, you won't burn in hell. Nobody will even tut-tut. Yet how much nicer it is for you, and your itamae, if you show respect for the codified ritual that has grown around sushi since the eighth century.
You order sushi from him (it is usually a him), and let him recommend the fish and the order in which it is served – probably white fish first, then oilier fish like tuna and salmon, ending with richer luxuries such as ikura (salmon roe) and uni (sea urchin). Any soup, drink or non-sushi orders go to the wait staff.
The ultimate sushi is nigiri, hand-shaped fingers of vinegared rice (known as shari) and topping (known as neta). There are those who say it must be eaten in the hands, and others who say it must be eaten with chopsticks. Find your own path. Just don't dip the rice side into your soy, or it will fall apart, and be sure to eat it in one bite. In this way, you respect the craft of your itamae, and preserve the integrity of his creation. And save your shirt from soy-stained rice droppings.
If you are offered an oshibori (hot towel), use it, then neatly fold the towel into its original shape. And don't mix the wasabi – that deliciously hot green paste that makes you feel like you are breathing fire through your nostrils like a dragon - into your soy sauce. The ginger (gari) doesn't go on top of the sushi, but is meant to refresh the palate between bites. The accompanying miso soup should be sipped straight from the bowl, held in two hands, and sake should always be poured by you for your companions, and poured by your companions for you. Unless, of course, you're dining on your own, in which case you are your own companion, so just keep pouring.