The Basic California Roll.
If you are going to introduce someone to sushi, this is the way to do it. A California roll contains crab meat, avocado, and cucumber.
Spread about a cup of rice on the sheet of nori, leaving about an inch of uncovered nori at one side. Do not pack the rice, rolling will take care of that. The rice should be less than a 1/4 inch thick -- you should be able to see nori through the rice. The biggest mistake is using too much rice.
Put avocado slices on top of the rice first, one slice thick, near the edge of the rice, the edge opposite the uncovered nori. Unwrap and split a piece of imitation crab meat lengthwise into two pieces. Place the two pieces end to end on top of the avocado. Then add several strips of cucumber next to the crab and on top of the avocado. (If you put the avocado on last, it is a lot messier to roll.)
I prefer to place the nori on a sheet of plastic wrap on top of the bamboo mat, to keep the avocado and rice out of the mat. Slowly fold the mat over, tucking the end of the nori to start a roll. (Keep lifting up the mat and plastic wrap as you go.) Lessen the pressure slightly to straighten out the roll, if needed. Then continue rolling with medium pressure.
Remove roll from mat and cut into 6 or 8 even pieces. Important Tip: Keep the knife very moist to prevent sticking, remoistening before each cut. First cut the roll in half, then fold the two halves together and cut into thirds (6 pieces) or quarters (8 pieces). Sushi bars usually serve the roll sliced into 6 pieces, but 8 is easier. Turn the pieces on end and arrange on platter.
Tip: Sometimes, if the end pieces are quite uneven, the ends are cut off at the one-third point and stood on end. Then, the other section is cut in half at a slight angle. All pieces will then look more alike when stood on end.
Some sushi bars make an "inside out" California roll. The rice is spread over all of the roll, there is no uncovered edge as above. Then the nori is turned over onto the plastic wrap so it is rice-side down. The ingredients are placed on one edge and the roll is rolled as before. After rolling, the roll is rolled in toasted sesame seeds prior to cutting, or sesame seeds can be sprinkled on top after cutting. Optionally, flying fish roe can be used in place of the sesame seeds (it actually tastes better, but sesame seeds are easier to find).