You can keep your rice from clumping and sticking together by washing it a few times until the water runs clear and then set it aside for 20 minutes or until no water remains. Washing the rice rinses a lot of the starch off of the rice which allows it to cook without clumping.
Source: Tips for Cooking Rice
Depends on what type of rice you’re cooking. Longer, thinner-grained varieties like Basmati are less sticky and starchy, and cook up looser. Shorter, fatter-grained varieties such as Japanese rice or glutinous rice (so-called because it is gluey—it contains no gluten, like all rice) are more sticky and starchy. In fact, glutinous rice is called “sticky rice” and is used to make joong/zongzi.