Simple Nori Rolls

Wash and dry the rice. Cook according to the instructions on the package. Meanwhile, combine the vinegar, sugar, and salt in a small bowl. Place the rice in the bottom of a large, shallow bowl. Drizzle the warm cooked rice with the vinegar mixture, stirring gently until the mixture is smooth.Cut the tuna into 1/4-inch x 1/4-inch x 7-inch pieces (about the width of your pinky). Slicing large fillings, such as shrimp, can make rolling out easier. Set aside.Cut the nori leaves into 4 5-inch x 7-inch rectangles. Place the nori on a bamboo sushi mat. Spread 1/2 cup of the rice mixture on one sheet of nori, leaving a 3/4-inch-thick strip of nori uncovered on the long side.Arrange the tuna and desired filling in the center of the rice. Secure the filling in the center of the rice and roll up the bamboo mat, pressing lightly until the rice and nori cover the filling. Stop rolling out at the end of the protruding nori strip. Lift the bamboo mat slightly and flip the nori roll slightly so that the uncovered nori strip fits snugly against the roll. Press down the mat to seal the roll.Cut the roll in half with a sharp knife, then each half twice to make 6 pieces of the same size. Repeat with the remaining rice, tuna, nori, and toppings. Serve with soy sauce, wasabi and ginger, if desired.