The trick with rice and pasta is not to stir it much at all. Stirring it causes starch to come out into the cooking water. With pasta this means you have to boil a kettle to rinse it when it is cooked, with rice it means disaster.
Pasta
This is easy. The only thing that can really go wrong is over-cooking. Pasta is cooked when it is still a little chewy. The stuff with round holes through the middle should still have round holes when it is cooked. If the holes collapse, you've cooked it too much.
Add the pasta to boiling water, to which you have added a half teaspoon of salt (if you like salt) and a little vegetable oil. The oil helps prevent the pieces sticking to each other.
If cooking spaghetti, hold a bundle at one end and lower the other end into the boiling water - it will soften very quickly and as it does, push the bundle down into the water. This is much better than breaking the spaghetti into pieces.
When you add the pasta to the water stir it gently to separate the pieces. When it starts to boil again turn the heat down so that the water is just bubbling gently. Don't stir the pasta after this. It should take about 10-15 minutes to cook depending on the type you use. Drain the water off immediately as it will cook further if left standing in hot water. A sieve or colander is best for this.
Rice
Long-grain rice is generally preferable as an accompaniment to savoury dishes. Basmati is my favourite and Thai jasmine rice is good if you can find it. The short-grain stuff is better for soups and puddings.
Good quality rice can often be cooked without rinsing first, but if it looks chalky or dusty it is best to rinse it in cold water. You need a sieve to do this well.
Put the rice in a pan with cold water - I cup of rice to 1.6 cups of water - and add salt if you want. Give a gentle stir to separate the grains. Bring to the boil then turn the heat down as far as it will go. Give another gentle stir and cover the pan. It should take about twenty minutes to cook. Try to keep the pan covered and don't stir the rice at all. Test it by lifting a few grains out with a fork and tasting them. When it is ready, turn off the heat and leave it to sit for a few minutes. Give it a stir to loosen it up and if it is still a little wet, leave it in the pan with the lid off to let the steam escape for a few minutes before serving.
Brown rice takes longer to cook and requires more water. Use about 2.4 cups of water to one cup of brown rice and cook for 50 minutes to an hour.
To reheat cooked rice, put the rice in a colander or sieve and sit it on a pot containing about five cm of water. Use the lid from the pot to cover the rice. The pot should be just a little bit smaller than the colander (or sieve). Bring the water to the boil and let the rice steam for five minutes or so (This is a good way of steaming vegetables too). Left-over rice can also be fried, perhaps with the addition of some finely chopped vegetables and soy sauce. Click here for a 'vegetable fried rice' recipe.