Place the rice into a mixing bowl and cover with cool water. Swirl the rice in the water with your hand, pour off and repeat 2-3 times or until the water is clear. Rinse a few more times.
After the rice is rinsed, let the rice drain in a colander or strainer for 1 hour.
After the rice has drained, put the rice in the rice cooker with the 3 cups of water, cover, and start.
If you don't have a rice cooker place rice and water in a heavy saucepan over medium-high heat; bring just to a boil, reduce heat to low and simmer, covered, for 15 minutes. Turn off heat and let rice rest, covered, for 15 additional minutes.
While rice is cooking, prepare the vinegar mixture. In a small saucepan over medium heat, combine rice vinegar, sugar, and salt. Heat mixture just until the sugar dissolves (do not let it boil). Remove from heat and let cool to room temperature.
When the rice is done cooking, gently spread out the rice over a cookie sheet. Evenly distribute the cooled vinegar mixture over the rice. Gently turn rice over from time to time with rice paddle or wooden spatula so that rice cools evenly.
To speed things up, fan the rice each time you turn it over. When rice has cooled to room temperature, it is ready to use for sushi rolls!
If you want to wait a little bit before making your sushi or while you are making the rolls, you can keep the rice at the right temperature by placing it in a large bowl and covering with a damp kitchen towel.