Are you plopping sauce right on top of your pasta as soon as you finish cooking it? As chef Andrew Carmellini would say, "You're doing it all wrong."
Most people dump out their unwanted pasta water and immediately start pouring cold water over the pasta, Carmellini explains in this Chow pasta tutorial. Both actions are major no-nos. First of all, the cold water actually rinses the pasta of starch, which helps thicken your sauce. Secondly, you'll want to save the excess pasta water and add it to your sauce later.
The correct way to cook pasta and sauce is actually quite simple. Immediately after cooking your pasta, put it into your sauce pan, and heat both up together. After the mixture has been cooked for about a minute, add a little of your leftover, starchy pasta water for that "shiny, yummy flavor," Carmellini says.
Cook for another minute, turn off the heat and then add butter, olive oil and cheese. Top your dish off with herbs if you'd like, then mix. Voilà! Now you're ready to eat.