These are the sushi rules, folks; rolled up in nori and sliced into bite-size morsels.
1) Eat lighter fish before fattier fish.
It's like tasting wines -- you start with lighter wines and finish with big, heavy palate-busting wines. When you're eating sushi, it makes perfect sense to start with lighter, more delicately flavored pieces of sushi and work toward the richer, fattier, more strongly flavored fishes, like eel or fatty tuna. It's palate preservation, plain and simple. But in the same way you're always free to drink a cab before a Chablis, you can ignore this sushi rule all you like. It's really more of a suggestion.
2) Don't mix the wasabi paste into the soy sauce for dipping.
Sushi purists love explaining that mixing together wasabi and soy sauce is not how it's done in Japan. Sushi savants insist that you apply a dab of wasabi on the side of a piece of sushi and then politely dip the sushi in a little soy sauce -- just not on the rice side! This rule was made to be broken. Go for it.
3) Don't soak your sushi rice in the soy sauce.
It's not marinade. Whether or not you've ignored the rule about mixing wasabi into the soy, this rule holds. In Japan, the sushi eating public tends not to dunk the rice at all. Instead, the soy sauce touches the fish part of the sushi. Why? Because sushi rice has a delicate flavor all its own, which is obliterated when you soak the rice in soy sauce like a sponge.
4) You can use your hands to eat sushi.
Ok, this is that rare rule that we absolutely love following. Go ahead, pick up the sushi with your fingers, give it a little dunk, then stick it in your sushi hole. Or use your chopsticks. Either way, fingers or sticks, the sushi rulebook is working in your favor.
5) Don't attempt to slice a piece of sushi in half with your chopsticks.
A chopstick isn't a saw. It's not even a butter knife. If the sushi pieces are too large for your elegant mouth, ask your server if the sushi chef will cut it in half. They have a ridiculous set of very sharp knives.
6) Don't play air drums with your chopsticks.
At least try not to. This is difficult for anyone with a basic sense of rhythm, harder still for anyone of whom it's ever been said, "You rock!" One day, science will confirm that holding a pair of chopsticks triggers a genetic response to play air drums. Until that day -- and even after -- try your best to resist the urge.
7) Sushi is not take-out food.
Sushi is all about freshness and presentation. Sushi is art that you eat. It's the perfect food for unhurried, mindful, appreciative eating enjoyed at a table like a civilized person. Which is to say, eating sushi is not like pulling a cheeseburger from a paper bag and scarfing it -- still half in its wrapper -- from behind the wheel as you battle epic traffic on the 405. Slow and steady wins the race.
As you probably noticed, the Sushi Rules come in two basic flavors. The first category concerns rules of respect, which are aimed at helping the customer achieve an appreciation for the care and artistry at work behind the sushi counter. Other rules, though, are essentially matters of personal preference and/or prejudiced opinion...you can fudge on these with a more-or-less clear conscious. They key is knowing which is which.