Did you know that, there is a grain for every recipe ?
It is better if you use:

Round grains for soups and sweets.

Medium grains for croquettes, "sartù" ( Naples rice timbale ), timbales and traditional risottos.

Long grains, such as Arborio, Carnaroli or Baldo, for refined risottos, great cook's favourites.

Unrefined grains, rich in fibre and nutritive elements, perfect for health cooking.

'Parboiled' grains ( which don't overcook ), the "intelligent" rice, rich in vitamins and mineral salts, best ally for people that don't have much time. Excellent for the preparation of well husked salads.

According to the different varieties, to the different grain types and to what we need it for, you prepare rice with different water quantities.
In general, to cook common rice, you need three times of its weight quantity.
The more rice quality is good, the more you need to cook it: actually, 15-20 minutes for the commonest rice type; 30-35 minutes, for the most refined. You must also consider that, unless you suddenly put rice, under cold water jet, it keeps on cooking on his own, even if it is no more on flame.
So, you must take rice away from flame, just some seconds before you serve it.

Also quantities vary, according to what we need rice for...
To prepare risottos, starters, side dishes and sweets, you must estimate 100 grammes of rice per person; for soups, you must halve quantities.

You must always pour rice on boiling water, neither cold, nor lukewarm, otherwise cold water makes grain crumbling.

Even if you pour other liquids, while cooking, be sure they are hot, otherwise cooking water would get cold, making rice losing consistency.

To avoid "undesirable animals" coming, you must, always, keep rice within thin cloth bags or in closed glass pots.

You must not wash rice before cooking, otherwise it loses part of its active principles, like mineral salts or vitamins.