Last week, Quest magazine, coddler of heiresses, financiers, and other layabouts, published its annual "Quest 400," the exhaustive yet unexplained list of the society fixtures it deems worthy. Originally the "400" represented the number of guests Mrs. Astor could fit into her ballroom. Mrs. Astor is long gone, so how can one land a spot on the list today? We looked through all 20 pages to find out how to make the cut.