[I'll get crazy with ese and toss some ham in the frying pan]
First-rate sushi experiences begin with knowing ...
... what appeals to you
... how to overcome tendencies of certainty with regard to the above
... how to leverage "informed" opinions of what is "best"
... how to keep loyalties from limiting your ventures
... that "knowing" may not always be the most crucial dynamic; engage/play
Other factors might include:
freshness (isn't this a given? if you "smell" fish, bail - period)
texture (for some patrons, not all goodness is melt-in-your-mouth buttery)
provenance (fish sourced from Japanese markets appear to have cache ...if locally caught, in-season varieties holds your interest they may very well be worth the premium they command)
age (some fish have noticably distinct flavor profiles as they mature ("shusse-uo"))
seasonality (corn is currently available at the local farmers market - it's also available year-round in most freezer aisles ... leaving cultural aspects aside, certain fish *may* hold greater appeal when taken during specific times of their migration cycle ... the fact that some of these specimens are sourced from various currents around the globe adds nuance to this element ("shun"))
treatment/cut (fresh off the hook saba is wonderful - less so maguro ... sourcing, prepping and knife craft can take on signature distinction in better shops)
aesthetics (eye appeal - picture this: vibrant, mechanical cuts nestled on symmetrically arranged ohba - poke)
environment (Sex in the City glamor bustle, service sector/expense account deal hush, loose tie salaryman carousing venues, shrine-like HNW emporia doling dollops of beluga and slabs of foie - note that within these coarse, generalized categorizations there are establishment where the tone alters with the time of day/evening)
pace (leisurely, chatty sprawl to heads-down fast 'n furious delivery; streamlined full-geta drop or piece by piece request and preparation)
the itamae (sets the stage - you'll click with some, less so with others ("inase"))
Akitist is correct. Su = vinagar; shi = rice. "Su-meshi" = seasoned rice. The first key variable is perfectly cooked and then seasoned rice. For traditional makizushi, the keys are perfectly prepared ingredients (combinations of egg, cucumber, konnyaku, carrot, shiitake, kamaboko, takuan, and so on), good relatively fresh and slightly toasted nori, and rolling technique that, together, result in the right combination of flavor, texture, temperature--the universe in two or three bites. Other common sushi then include chirashi (the very common boxed sushi), inarizushi (sushi in aburage, my fave), the old traditional oshozushi, onigiri or musubi (which actually does not use sumeshi, my other fave), and, of course, nigirizushi--that which Americans equate with sushi.
Nigiri is simple: perfect sumeshi and perfect sashimi.
re: Sam Fujisaka
Sam, "nigiri" is by far and away, the vernacular equal to "sushi" in Japan. I understand the constant reenforcement of the definition of sushi as vinegared rice and the broader inclusion of other items as also being a type of "sushi"- i.e. chirashi, inari, maki. But nigiri-zushi is usually the implied subject when "sushi" is discussed in Japan- not just Americans.
Makizushi ("rolls") are most often served as stomach stuffers at the end of or as a supplement to, sashimi and nigiri meals. Chirashi is often boxed for bento meals, but it just means something like "scattered". It's served in bowls for lunch as well.
First rate sushi (nigiri) starts with and depends on fresh, good quality seafood that has been handled properly at every stage from hook to slice to serve. It is often the very precise demands of where something was caught and how it was handled, that makes seafood from Tsukiji central fish market in Tokyo such a desirable source of quality neta for sushi chefs internationally. This is a sort of "branding" phenomenon it seems. This has also extended to fish caught from particular parts of the ocean (perhaps a natural market preference that developed), but also to fish farms, that are deliberately breeding, branding, and marketing fish. So really, before the chef's knife work and yeah, yeah, the quality of the rice and balance of vinegar, it starts with the acquisition of fine seafood. And most of it should have a pedigree if it was farm raised or a natural history of some sort, that you can learn to understand what and why some sushi is better than others.
Silverjay, you are, of course, 100% correct in everything you say. It is just my quixotic quest to try, first, to indicate to Americans that sushi does not equal sashimi; and that there are other types of sushi besides nigiri. I make in about equal parts inari, maki, musubi, and nigiri. As a fisherman and cook, I've worked long and hard to turn my catch into well sliced sashimi and hopefully even better nigiri. As to what people do in Japan: I go there and say to myself, "These people aren't Japanese!" Stupid, I know.
re: Sam Fujisaka
Sam, as usual, has it spot on. As does Akitist. (Except, Sam, I thought boxed sushi is the pressed form called oshizushi...)
If the rice interests you, take a bite without the topping. Does the rice hold together with grains still separate? Do you like the taste/smell (amount of vinegar, sweetener, salt)? If you get into it you'll start to notice finer distinctions, such as how the flavors vary with the types of vinegars and sweeteners used, what the rice was cooked with (i.e., kombu), etc. Most people don't care about that detail -- life has other priorities after all -- and if you're happy without being such a rice nerd (no offense, you-know-who - I - mean) then you're probably better off.
For the fish, the usual fresh fish principles apply -- smell, appearance, etc. With raw, watch for stringiness from the fascia (a type of connective tissue), great appearance, good rice to topping ratio (with nigiri). A good way to develop is to get chirashi, toppings scattered on a bowl of sushi rice - easier to taste separately.
There are, as I'm sure you're aware, one or two more things available to learn. For me the most important is to be easy to please but difficult to impress. If I care to pay attention, I can always learn stuff -- good, bad, whatever.
You have to get down to the basics. Sushi means something like vingar-treat. Based on vinegar-flavored rice. You can have fishless sushi, made with natto, shredded cucumber, various pickles, egg (sort of between scrambled and custard): all traditionally Japanese.
Top-grade sushi requires top grade rice, prepared properly. Not for nothing does the apprentice sushi chef learn to prepare the rice before picking up a knife.
Best-quality fish is also very important, of course. But if all you're interested in is the fish you might as well skip the rice and just order sashimi.
1) texture. Does it melt in your mouth?
2) cut. Are the pieces cut nicely, not chunks or giant slaps? Sushi is not supposed to be bulk food, but have finesse.
3) freshness. Sushi is not supposed to have a fishy smell -- if it does, it was either thawed improperly, or has been around too long.
4) color -- if tuna is too red (like the color of the Chowhound wallpaper) it's most likely dyed.
5) presentation. Are the chefs taking an interest in what they do, or are they simply churning it out? Is there some thought that goes into the way it is presented?