Jennifer Aniston's ponytail looks as perfect with a tank as it does with a tux. The secret to its versatility? "We keep the sides super-sleek and add piecey volume to the crown," explains her hairstylist, Chris McMillan. To get the look, gather hair into a low pony and secure with a thick elastic. Then split the tail in two and pull both ends to tighten the sides and loosen the roots.