Long, flowing hair is a great match for strapless formal dresses because it brings so much attention to the face and upper body.
Long hair also adds a youthful twist to formal wear (unlike a stiff updo) so it's a great way to look updated and modern.
Here's how to wear long hair with a formal dress:
Keep the volume under control with products designed to add texture and shine: structured curls (the kind you get with old-fashioned hot rollers) are out. Instead, opt for long loose waves or silky, stick-straight hair.
Long, sexy hair becomes the accessory, so go easy on other jewelry around the face. Earrings -- which need to be oversized diamond studs or chandelier earrings to be seen with long hair -- are all you need. Skip the necklace.
Take daytime hair into the night with a beautiful hair ornament or a look that is partially pulled up or back away from the face.