While the dum process, check the rice in between and if you notice that the rice is not cooked properly, then the simple tip is too add some water all over the rice. If it is too undercooked, add a cup of water. If it is slightly undercooked then just add 1/4 cup to 1/2 a cup water all over the rice. Seal the lid tightly immediately and let it dum until the rice is done.