Celebrity couples aren't always models of marital stability, but as Christie Brinkley, A-Rod, and Madonna join forces to hold the planet hostage, New York Times columnist Maureen Dowd goes off in search of those telltale signs of who to avoid ending up at the altar with. She finds her answers in a 79-year-old Catholic priest, Father Pat Connor, who's been giving a "Whom Not to Marry" seminar for 40 years. Avoid swapping rings with: