First, choose the correct type of dry pasta. Elbow macaroni holds up well to thick, creamy sauces and is less likely to clump than other shapes of pasta. And, second, be sure to cook the elbow macaroni a couple of minutes shy of the package directions so that it will finish cooking to a perfect al dente in the oven. If you cook the pasta to al dente before baking it with the cheese sauce, it will likely end up mushy and sticky after baking.