Summarize:

Use a ratio of 2 parts water to 1 part rice. If, for instance, you're cooking 1 cup (240mL) of rice, use 2 cups (470mL) of water. Pour the water into a medium pot, add a pinch of salt, then bring it to a boil over medium-high heat. If you want to make 4 servings, use 1 cup (240mL) of rice and 2 cups (470mL) of water. Divide those measurements in half to make 2 servings or multiply them by 2 to make 8 servings. Just stick to the 2 parts water to 1 part rice ratio. Stir the rice, reduce the heat to a simmer, and cover the pot. While American-style converted rice is precooked, other parboiled varieties actually need to be cooked longer than regular white rice. These varieties need to be cooked for around 45 minutes. If you soaked the rice, check it after about 35 minutes. If you're not sure which product you have, check its cooking instructions.
Bring 2 parts water and a pinch of salt to a boil. Cook South Indian-style parboiled rice for up to 45 minutes.