Steamed Nishiki Rice

Put the rice in the rice cooker bowl (or a fine mesh strainer set in a bowl) and cover with cold tap water. Swirl it with your hand, the water will turn cloudy white almost immediately. Pour it off and repeat.
Wash 4 to 6 times, until the water runs nearly clear. It always takes more rounds than you think. This is the step people rush, and it's the one that matters most. You're rinsing off the surface starch that makes rice gummy.
Drain the rice well and let it sit in the strainer for 15 to 30 minutes if you have the time. A short rest lets the grains hydrate evenly. Not strictly required, but it earns its keep.
Add the rice to the cooker and pour in the filtered water. For a rough manual ratio, use about 1 part rice to 1 to 1.1 parts water; if your cooker has fill lines, use those instead. Start on the low end. Nishiki likes to be on the firmer side, and you can always add a splash next time.
Cook on the standard white-rice setting and let it finish its full cycle. When it's done, don't open it right away. Let it steam, covered, for 10 minutes off the heat.
Fluff gently with a rice paddle or fork, cutting and lifting rather than stirring so you don't smash the grains. Serve hot.

No rice cooker? Same wash, then combine the rice and filtered water in a heavy pot with a tight lid. Bring to a boil, drop to low, cover, and cook 12 minutes. Off the heat, rest covered 10 more, then fluff.
This is plain steamed rice, not seasoned sushi rice. If you want vinegared rice for rolls or nigiri, season it after cooking.
Filtered water genuinely matters here. If your tap is heavily chlorinated, you'll taste the difference.

Ingredients