A bowl of hot pasta misses the mark catastrophically if the noodles come out of the pot sticking together or, worst of all, knotted up in gummy clumps. The problem is pot space: Noodles need room to release starch and cook evenly. Pasta absorbs nearly double its dry weight in water. If the noodles don't boil in enough water, sticking happens. A shallow boil also means very starchy water, which makes for gluey noodles. Adding some oil to the pot isn't an ideal deterrent to sticking; it makes the noodles too slippery for sauce to stick.
The solution: Use plenty of water, about 5 quarts per pound of dry pasta. Give the pot a stir as soon as you add the pasta to help keep the noodles separated when they plunge in. Boil vigorously until al dente. Drain the pasta (never rinse), and do as chefs do: Finish the last bit of cooking in the pan in which you've made your sauce. The noodles absorb more flavor this way, and everything just marries together nicely. Add a little reserved pasta cooking water if the sauce becomes dry.