Grasping the pasta-sauce connection is one of the keys to a fundamental understanding of pasta dishes. Pairing an angel hair pasta with a cream sauce will result in a gloppy mess, while putting rigatoni with a light tomato sauce will leave you with a pasta that dominates its sauce instead of forming a partnership. Its best to sauce the pasta before its plated, either in the pan in which the sauce was made, or in a separate bowl, this will ensure complete incorporation of the sauce and will allow the starch from the pasta to lend a little body to the sauce. It should also be noted that cream sauces are at their best when combined with a fresh pasta, since the cream needs to be absorbed. If you use a dry pasta with a cream sauce take care to give the pasta a good bit of time in the pan with the sauce. Tangentially, when ordering penne in Italy, be sure to pronounce it like "pen-nay" as ordering it as simply "penee" means you're ordering a nice steaming dish of penis.
Shaped pastas work very well with many different types of sauces. However, a very chunky sauce, such as a Farfalle Pasta With Wild Mushrooms, is best suited for a shaped pasta. These shapes have lots of lovely nooks and cranies with which to capture the pieces of meat or vegetable.
Examples of shaped pastas:
Tube shaped pastas go well with sauces that are thick or chunky, like pasta with broccoli and red pepper. Keep the size of the ingredients in mind: some smaller shapes won't hold the ingredients, others may be too big for a simple sauce. I like ridged pastas a lot because their texture gives the sauce lots of surface area to cling to.
Examples of tube shaped pastas:
Well that leaves us with the long noodle pastas. These pastas have a great amount of surface area and therefore are best partnered with an olive oil based sauce. The oil serves to keep the pasta unctuous and does not overwhelm the pasta. A thicker noodle, such as fettuccine, stands up to a cream sauce or a ragu, while the thinner strands are best with a lighter and thinner sauce such as tomato vodka cream sauce.
Examples of long noodle pastas:
mkb says we say GRAVY not SAUCE and we viciously dress down anyone who dares cross us. *roar*