Britney Spears, Lindsay Lohan, Hilary Duff—they all grew up too fast. Now Miley Cyrus, 15, could lose her tween tiara, too, after appearing in a racy Vanity Fair shoot spread. But if Cyrus wants to stay on top, she needs to learn to walk a tightrope. Advice No. 1: Go back to acting like a kid, even when you feel like an angsty teen. No. 2: Stop saying you love "Sex and the City." No. 3: Starting hanging out more with your girlfriends, and less with your achy-breaky, semi-creepy dad.