The question that has plagued me forever: Do you time pasta as soon as you add it to the pot or once the water begins to boil?
Water should be vigorously boiling before you add the pasta. For a whole pound of pasta, add a handful of salt, then add the pasta, and then start counting. I always need to turn down my heat after adding the pasta, as my stove gets crazy.
I time as soon as I add it. I start checking for doneness about 2 minutes before the recommended cook time (assuming dried pasta), then every 30 seconds or so until its ready. I hate, hate, hate overcooked pasta.
I use a method that makes sense only to me - put it in the water, set the time with an additional minute added, start tasting 2 minutes before the timer is done and invariably drain it before the timer is up. I know, kinda dopey.
Start timing as soon as the dried pasta hits the salted water, if it is fresh pasta as soon as one or two noodles start to float start the timer for two or three minutes. With fresh made pasta I always taste for doneness after about a minute. For dried pasta I always end up turning down the heat after it begins to boil because I don't want starch water boiling over.
Salted water (salty like sea water, so LOTS of salt) should be at a furious, rolling boil before the pasta hits it, regardless of whether you're using fresh or dried pasta. You must use copious amounts of water, too, or the pasta will stick to itself. In some cases, the water will go off boil when you dump in the pasta. In that case, start timing from where it returns to the boil. Use a large enough pot (a stock pot or canning kettle is ideal) and you won't have a problem with boil-over. Start tasting at least a minute before the recommended time. When it's done to your taste, turn off the heat, and dump in a cup (8 ounces) of cold tap water to stop the cooking. Drain, do not rinse. Save some of the pasta water if you're making a sauce like a pesto, or other "dry" sauce (usually don't need it for tomato sauces, but it couldn't hurt to save some), about a cup, before draining. This will help loosen your sauce, and the starch will help thicken the final product.
I'd say you've already recieved good advice so far except that I don't "drain" the pasta. In Italy they use a very light touch with sauce. It's not smothered as in America al Buco di Beppe, so it get's scooped out al dente directly into the sauce to finish. The cooking times on the package are just a "suggestion". There are more than 2,000 recognized pasta shape in Italy and they all have a purpose.
I never time pasta when I cook it. I tend to just start checking for doneness when I feel like it's been boiling for a while...
You got great advice. There's not much to add. Just remember to start checking early, and check often. (Sounds like the advice for voting.) I take the pasta out before it's quite the al dente I am looking for, because it does continue to cook. I usualIy have a pot of whatever sauce I am making on the stove. I like to add the pasta to that to absorb the flavors. The pasta will also continue to cook in the sauce.
I believe mrslarkin gave you the answer you were looking for. I never add pasta to the salted water until it's at a rolling boil, then start timing it from there. As most of the others stated, start checking for doneness about 2 minutes before the package's recommended cook time. For fresh pasta, it's going to depend on the thickness of the dough, but still not added until the water is boiling hard.