Pasta should not be stirred much at all, as it causes starch to come out into the cooking water. Otherwise cooking pasta 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). You can add a little vegetable oil. Some people say it helps prevent the pieces sticking to each other. I'm not sure if that's true.
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.