Japanese cooks sometimes vary the following recipe by adding a tablespoon of
sake to the rice water, or changing the amounts of sugar and vinegar to suit their tastes. Dried, packaged konbu, "kelp," is available in Japanese 
markets along with regular rice vinegar and sushi su, a rice vinegar made just for sushi rice and already flavored with salt, sugar, and MSG. 

2 cups short-grained rice

2 cups water

1/4 cup rice vinegar

1 tablespoon sugar

2 teaspoons salt

3" square of konbu

Thoroughly rinse the rice until the water runs clear, about five 
minutes, and let it drain in a colander for an hour. Usually, Japanese 
rice is coated with a cereal powder that must be washed off, even 
though the package may say it isn't necessary. When the rice is cleaned, 
put it into the pot. Clean the seaweed with a damp cloth and cut fringe
into one side to help release the flavor. Bury it in the rice. Add 
the water, cover, and bring to a boil over high heat. Remove the seaweed 
just as the water boils or it will flavor the rice too strongly. Reduce the heat to medium and cook for five minutes, then reduce to low and cook fifteen minutes without removing the lid, even for a peek. When the rice makes a dry crackly sound, remove it from the heat and let it
stand covered for another ten minutes.

While the rice is cooking, combine the salt, sugar, and vinegar 
in a small saucepan. Heat and stir the mixture till the sugar is dissolved, then allow it to cool. (This is not strictly necessary, since rice vinegar usually already contains salt and sugar.)

Turn the rice out into a shallow wooden bowl. The wood helps absorb the
moisture. Do not use anything metal, as it may react with the vinegar and
create a bad taste. Add the vinegar dressing a little at a time, cutting it 
into the rice with the rice paddle or spatula [1]. Use a horizontal motion to
keep from  bruising the soft rice grains as they cool. Every so often, dip
the spoon into cold water  to keep the rice from sticking to it. While you're
stirring the rice with one hand,  cool it with a fan held in the other, which
will make it glossy [2]. An electric fan or a live  assistant makes this
process easier. It takes about ten minutes either way.

Sushi rice can be kept for several hours at room temperature,  covered with a
damp cloth. It should not be refrigerated and should be eaten the same  day
it is made. When you are ready to make the sushi pads, have a little bowl of 
vinegar water (one-third vinegar, two-thirds water) ready to dip your fingers
into to  keep the rice from sticking to them. Put a couple of tablespoons of
rice into your right hand  and press it firmly into an oval shape, using the
first two fingers of your left hand  [3,4]. Remember, this little maneuver
only took the chef a couple of years to perfect.

Basics of rollmaking

Place a nori sheet on the mat, with the glossier side down. Spread a thin layer of rice over the nori with gentle motions of the wooden paddle. Keep the paddle slightly wet to keep the rice from sticking. The layer of rice should be about two rice grains thick. Leave a "margin" of about half an inch of nori uncovered with rice.

Smear a thin line of wasabe over the rice at a distance about 1/4 of the width of the nori sheet.

Cut the ingredients: cucumber is cut into thin sheets and then lengthwise into thin strands; avocado, crab meat, tuna or salmon is cut into thicker strands. Place the ingredients along the wasabe line parallel to each other, shifting them toward the center of the sheet. Moisten the "margin", tapping it lightly with water. 

Wrap the nori sheet around the ingredients from the near side, and keep wrapping it with the mat, pressing firmly onto it, until it is completely wrapped around. Hold the wrapped mat for a few moments, allowing the nori to glue together. Place the roll onto a cutting board and cut into short segments.