Step #1 In a fine strainer, rinse rice under cold running water until water drains clear, 5 to 10 mins.
Step #2 Put rice in a 2- to 3-quart pan & add 1 1/2 c water.
Step #3 Bring to a boil over high heat, then lower heat to maintain a simmer.
Step #4 Cover up & cook this until water is absorbed, 10 to 15 mins.
Step #5 Meanwhile, in a small bowl, the sugar, stir 1/4 c rice vinegar, & salt until sugar & salt are dissolved.
Step #6 Spread rice out in a shallow 12- by 16-inch baking pan & slowly pour vinegar mixture over it, turning rice carefully & fanning it until it comes to warm room temperature, about 10 mins.
Step #7 Mix remaining 1 tbsp rice vinegar with 1 c water.
Step #8 Pour into a small bowl to moisten your hands (so rice doesn't stick) while rolling sushi.
Step #9 Place a sheet of toasted nori, shiny side down, on a bamboo rolling mat (with slats running horizontal to you) or on a piece of plastic wrap (about 10 by 12 in.
Step #10 ), aligning long side of nori with the bottom edge of mat.
Step #11 Dip your hands in vinegar-water mixture & scatter 2/3 c rice over nori; pat into an even layer, spreading out to the sides & bottom of nori, but leaving a 2-inch-wide strip bare along the top edge.
Step #12 With your finger, spread a thin stripe of wasabi (about 1 tsp) horizontally across center of rice.
Step #13 Arrange four avocado slices along wasabi stripe (it's okay if the slices overlap or if some ends stick out), then arrange about 2 tbsps of the crab on top of the avocado.
Step #14 Moisten top edge of nori with vinegar-water mixture.
Step #15 Holding fillings down with your fingers, lift edge of mat closest to you with your thumbs & roll it over so that the near edge of nori meets the far edge of rice bordering the 2-inch-wide bare strip of nori at the top.
Step #16 Then roll bottom edge over to seal, & briefly press mat around roll.
Step #17 Remove roll from mat.
Step #18 If desired, trim off any filling sticking out.
Step #19 With a sharp knife, cut roll this into six or eight equal pieces, rinsing knife in water between cuts.
Step #20 Repeat process with remaining nori, rice, & fillings.