Use a big pot. Crowding pasta in a small pot can make it stick together, which keeps it from cooking evenly.
Choose your shape. Angel hair or spaghetti is best for thin sauces, such as a simple mixture of olive oil and garlic. Thicker pastas—fettucini or pappardelle—work well with heavier sauces, such as Alfredo. Short or twisted pastas like penne or gemelli are ideal for chunky sauces with large pieces of vegetables.
Salt the water. For best flavor, add a generous amount (2 tablespoons kosher salt to 4 to 6 quarts of water).
Hold the oil. Some cooks add it to the water so pasta won't stick together, but that means your sauce won't stick to the pasta, either.
Add pasta all at once. Do it quickly, and keep the heat high enough that the water rapidly returns to a boil. Reduce heat slightly if the water starts to foam at the top or begins to boil over.
Skip the lid. Pasta is more likely to boil over when it is covered.
Stir. Give the pasta a good stir immediately after putting in the boiling water, and stir again a few times while cooking to keep the noodles from sticking together.
Set your timer. Cook pasta to al dente (meaning "to the tooth" in Italian), which describes pasta that still has a little resistance when eaten. If the pasta will be baked after it's cooked, as in saucy casseroles, boil 2 to 4 minutes less than package directions suggest so it doesn't become mushy.
Drain, don't rinse. Running hot pasta under water will remove starches that help the sauce stick to the noodles. Exceptions: lasagna noodles, which can be hard to separate if not rinsed in cool water, and pasta being used in cold salads.
Save some pasta water. If your garlic or tomato sauces need thickening, add a little of the salted water the pasta was cooked in. It will thin the sauce initially, but starch in the water will help bind it as it cooks.