The key to cooking pasta properly is lots of water.  For every pound, use 20 cups (5L) of water.  Never use less than 12 cups (3L), no matter how little you cook, and don't cook more than 2 lbs. (1 kg) at a time.  Add up to 1 tbsp. salt, depending on the quantity of sauce and amount of pasta that will be added.  A tsp. of oil helps keep pasta separated, but it can make noodles slippery and prevent a cream sauce form clinging.  Keep the heat on high.  When the water reaches a full rolling boil, add the pasta all at once.  Immediately stir with a wooden spoon to separate the noodles.  To submerge long, brittle pasta, such as spaghetti, press down gently on the potion about the water until the strands are completely submerged.  Always keep the water boiling rapidly.  Don't cover.  Stir often.  

Timing
Frequent testing is the only way to avoid overcooking. "Al Dente" is the term frequently use to describe perfectly cooked pasta.  It means "firm to the bite" neither too hard nor too soft, firm but tender.  Once the water returns to the boil, fresh pasta need only a couple of minutes.  Dried pasta needs 6 to 12 minutes; taste after 6 min.  Remember, after draining pasta continues cooking.

Draining
Use a colander, tossing the pasta several times to shake off the water.  Do not rinse.  If you want the pasta to absorb a little sauce, an asset with a thin cream sauce, return pasta to the cooking pan.  Add the hot sauce and toss it with the pasta over med. heat for a minute or two.  Or turn the drained pasta into a large serving bowl, add the hot sauce, butter, oil or cheese and toss.