The rice, as you know, is the cornerstone to quality sushi – no matter how superior seafood you obtain (which is also very important), if the rice isn't done properly your sushi fails.
Always use a glutinous, short-grained, japonica rice, or else your rolls and other sushi construction will likely fall apart as soon as your guests pick it up. A good quality rice will not have too many broken grains. Rinse it several (at least five or six) times, let it soak for 15-20 minutes at least one of the rinse cycles.
Unlike long grain rice, most sushi rice instructions (including what I use) call for equal amounts water and rice, or closer to it than the usual 2 parts water to 1 part rice. Bring it to boil, cover it then let it cook on your stove's lowest setting. Cook it without removing the cover for about 12-15 minutes before checking for doneness.
For two cups of rice, use about 1/4 cup of rice vinegar, and approximately two or three tablespoons of sugar. I recommend using unseasoned rice vinegar and adding sugar to your taste rather than using the pre-sweetened stuff, so you can control the amount. Add a couple of tablespoons of mirin (Japanese cooking wine), optionally a pinch of salt to taste.
Combine the other ingredients while the rice is cooling to about body temperature (98F; 36C), then mix gently with the rice, being careful not to smash or break the grains,then assemble your sushi.
Eat the delicious sushi until you either explode, or need a crane to lift you away from the table.