The responsibility for great sushi extends to the customer.
The sushi bar diner is expected to order from the chef (but drinks and other food from the waiters), to pick up each piece with fingers or chopsticks (both are correct) and to eat it in one or two bites without putting it back on the plate.
Another sushi commandment, often flouted in American sushi bars, forbids dropping a piece of sushi into soy sauce and leaving it to soak. All the careful hospitality of the Japanese tradition could not conceal the shudder that ran through every sushi chef when asked about this practice. “It is very painful for us,” Gen Mizoguchi of Megu said.
For the record, you should turn the piece upside down and swipe the fish lightly through the dish of soy sauce. A small amount of wasabi can be added to the dish, but too much is disrespectful to the chef and the fish, as it drowns other flavors. [Moskin]
Moskin, Julia. “How to Eat Sushi.” The New York Times. 21 April 2004. <www.nytimes.com/2004/04/21/dining/21SBOX.html> (20 April 2004).