Jeggings: Slimtastic!

As in, jean-leggings... These super-slim pants are often manifestations of personality traits like being ultra-trendy and having a youthful flair. But, keep in mind that they are best worn by slim gals, says Sherrie Mathieson, style consultant and author of Forever Cool: How to Achieve Ageless, Youthful and Modern Personal Style. "Leggings are very useful since they have a ‘tights’ effect. They are great with voluminous, long and multi-layered tops."

Where to wear 'em: Legging-like jeans are great for fall if tucked into flat knee-high boots for a casual day or with high heels for a sexy date night.

Pictured: Lace Insert Jeggings ($90 at Topshop)