Believe it or not, preparing good rice is one of the most difficult things in cooking. There are too many varieties on the market, as well as a whole bunch of ways to cook them.
There is no exact ratio of rice to water, because different varieties absorb different amounts of liquid and this question cannot be answered for all. The exact proportion of the type of rice you're using usually marked on the package, so it's a good idea to consider it when cooking.
It is important to remember that standard rice absorbs about 2.5 times the volume of liquids and it turns out really good in the presence of more fat. Experts deny the practice that some chefs do, to fry the rice until it's transparent before boiling it.
They recommend boiling it on low heat under a lid in salted water with a little fat for about 15-20 minutes and it doesn't need to be stirred, so the grains don't to stick together. Then leave it on the heated hob with the lid on to absorb the liquid around it well.