Make sure that you rinse the rice, three or four times in cold water, until the water is running pretty clear. This removes the starch and helps to stop clumping.
Cover the rice in cold water about an inch and a half above the level of the rice.
Bring the water to the boil with the pan lid on and when boiling nicely, take the lid off for the remainder of the cooking time. It will not boil as vigorously with the lid off which is fine.
Keep an eye on the rice and when it appears to have boiled off the water, then you should be spot on!
Do keep an eye on it though - dont let it boil dry and add a little more water if it appears to have boiled dry but the rice is still bitey.
Best of luck - works perfectly for me every time :o)