Keep the fish in the refrigerator until ready to serve. Use a sharp fillet knife with a thin blade to trim any blemishes.
Then slice into long, evenly thick (1/4 to 1/3 inch) strips, cutting against the grain of the fish. Cut across the fish in a single stroke, rather than sawing back and forth, in order to avoid tearing the flesh.
Then half into smaller pieces, about the size of a domino.
Serve the pieces in a fanned out, overlapping row on a chilled plate with sides of wasabi and ginger and a small dish of soy sauce for dipping. Accompany the dish with a good Japanese sake (Japanese rice wine pronounced SAH-kay) or a light lager.