ET’s Thea Andrews is first on the set of the much-buzzed about “Cougar Town” for a little one-on-one with series’ star Courteney Cox, who fills the ET correspondent in on the litmus test for spotting a cougar. “You know you’re a cougar when you’re attracted to your son’s friends. You know you’re a cougar when you’re attracted to your daughter’s — who’s five — idols, which is where I come in,” Courteney jokes. Courteney’s daughter Coco is five and she has a huge crush on “High School …