Rinse the dry rice 3-5 times in very cold water.
Using a rice cooker, follow instructions given for making sushi rice. (This will probably be about 1 ¼ cup water for every 1 cup of dry rice.) Set to cook at given specifications. If not using a rice cooker, combine the rice with water in a medium saucepan. Bring to a boil, then reduce heat to low, cover, and simmer 20 minutes until rice is tender and water is absorbed.
While the rice is cooking, mix together rice vinegar, sugar, and salt. When the rice is done cooking, stir in the seasoning using a wooden paddle. Allow to cool uncovered, or use the paddle to transfer the rice onto a board lined with plastic wrap.
If using the rice to make sushi rolls, dip your hands in cool water to help prevent it from sticking to your skin. Use gentle pressure to mold the rice into shapes, or use bamboo rollers to form rolls.