Uber-stylist (and now full-fledged fashion designer) Rachel Zoe has been working with Cameron Diaz for a long time, so we got her to dish on our July cover girl's style. First, notes Zoe, Diaz trusts her own instincts. "From a fashion perspective, she's the most grounded person I've ever met, " Zoe told us. "She just wears what feels right." Click on the gallery for more of Cameron Diaz's style rules!