I've always made rice in a rice cooker. The one I currently own was handed down to me from my Mom, and it's the PERFECT size for me, since it makes just 3 cups. She loaned me her large, 10-cup cooker, but I pretty much always use my little model. It's nothing fancy like the new Neuro-Fuzzy or Micom models, but it has one job to do, and it does it well.
The cooker should have come with a measuring cup for the rice. However, this cup, as a Japanese cup is not the same as an American cup. A Japanese cup is 6oz, compared to the American 8oz. So, if you don't have a Japanese measuring cup, simply use 3/4 of an American cup instead.
Rice cookers are pretty idiot-proof; in addition to supplying the rice measuring cup, the pot will have lines indicating the water level.
The hardest part of making rice in a rice cooker is the washing and soaking. You can't just toss in some rice and water, flip the switch and expect perfect rice. So, here's how to do it the right way, for perfect rice EVERY time.
Measure out your rice into the rice cooker pot. Here, I'm using 2 Japanese cups (12oz total), so, if using American cups, use 1 1/2 cups.
Of course, make sure you're using Japanese rice; it's a short-grain rice, which is what makes it nice and sticky.
Rinse well under running water; make sure the water isn't too hot or too cold - you want it to be just in the middle. Swish the rice around with your hands, and the water will turn opaque and white.
Drain the water, then repeat the rinsing, swishing and draining about 2-3 times, or until the water almost runs clear.
Finally, drain almost all of the water, then GENTLY rub the grains together with the palm of your hands. Treat the rice as if it were ripe berries that you don't want to crush.
Rinse out the rice one last time. Transfer the rice to a mesh sieve and let drain for 30 minutes.
Place the rice back in the rice cooker pot and add water (just like with the rinsing, not too hot and not too cold). For however many cups of rice (Japanese cups), simply add water to the corresponding line. Soak the rice for about 45-60 minutes, then place the pot inside the rice cooker, close the lid, and turn it on!
Once the rice has cooked, your rice cooker should switch over to a "warm" setting. Don't open that lid!
Let the rice rest for about 15 minutes to allow the rice to finish steaming. Simply fluff with a rice paddle before serving, and you're done!