Whether you have guests coming for dinner tomorrow and want to impress them with your to-die-for homemade pasta sauce, or you're trying out a new recipe for pasta salad that calls for chilling it before adding the dressing and other ingredients, you can cook the pasta the day before and refrigerate it until you are ready to proceed with the recipe. Refrigerated pasta lasts for up to three days. Just be sure to use plenty of water and to slightly undercook the pasta, particularly if you will be incorporating it into a dish that requires further cooking.
Fill a large saucepan or stock pot with at least 4 quarts of water for every pound of spaghetti. Bring the water to a rolling boil over high heat and add 1 tablespoon of salt for each pound of pasta.
Remove spaghetti from the package and fan it out into the boiling water, working quickly so that the water continues to boil and moving the pasta around with a long spoon or fork until it is completely submerged.
Reduce the heat just enough so that the water doesn't boil over but is still boiling steadily. Keep moving the pasta around until the water has softened its outside starches, which will prevent it from sticking together.
Cook the spaghetti for about 7 minutes, slightly less time than the recommended 8 to 10 minutes, and turn off the heat. Pour the spaghetti immediately into a colander and drain completely.
Rinse the pasta under cool running water and drain it completely. Toss the spaghetti in just enough olive oil to keep it from sticking together during storage. Reheat the pasta the next day by plunging it for about 1 minute in a large pot of boiling water, then drain well and proceed with your recipe.