To cook spaghetti properly, follow these key steps:

1. Fill a large pot with plenty of water (about 4 to 6 quarts for 1 pound of spaghetti) and bring it to a rolling boil.
2. Add a generous amount of salt to the boiling water to season the pasta.
3. Add the spaghetti noodles to the boiling water and stir immediately to prevent sticking.
4. Boil the spaghetti uncovered, stirring occasionally, until it is al dente (tender but slightly firm to the bite). This usually means cooking for about 1-2 minutes less than the package instructions suggest—around 8-11 minutes depending on the brand.
5. Before draining, reserve some of the starchy pasta water if you want to use it to enhance your sauce.
6. Drain the spaghetti in a colander but do not rinse it; rinsing removes starch which helps sauce adhere.
7. Toss the hot spaghetti immediately with your sauce and serve.

Do not add oil to the pasta water or to the cooked spaghetti, as this will prevent sauce from sticking properly.