We all know that going gray can be aging. But there are several other ways your hair might be adding years to your look.

You have an all-one-length cut.

Without layers, your hair won't have that magical, youthful quality that stylists call "movement." Long layers remove weight from the bottom half of your hair so your style can swing and bounce. And while blunt edges accentuate lines in your face, layers have a softening effect. Consider side-swept bangs if you want to make your face look a bit rounder and your cheekbones stronger.

You have shelves full of styling products.

If you're using more than one styling product in an effort to make your hair look fuller, your plan may be backfiring. Mousse and gel and hairspray can give the hair lift for a few hours, but they also make it look stiff and sap its shine—a very aging combination. If you have a well-layered haircut that's not too heavy at the bottom, you won't need to load up on styling products to achieve volume. One dollop of lightweight mousse will do the trick; once hair is dry, use a drop of silicone serum to add shine.

You have dry, frayed ends.

As you get older, your hair loses not only pigment but also its ability to retain moisture. Keeping it smooth and glossy—hallmarks of youth—requires a little more effort. Do a deep conditioning treatment at least once a week, don't shampoo more than every other day, and get frequent trims to avoid split ends.

You have a deep, dark hair color.

Solid black or brown hair can highlight shadows on the face, drawing attention to lines and bags. If you're fair-skinned, a dark hair color also accentuates the contrast between your hair and scalp, which makes thinning more noticeable. A few highlights around the face and at the crown of the head add softness and make a dark hair color appear more natural. Don't dye your hair as dark as it was in your teens and 20s; a shade or two lighter will be more flattering in your 30s and beyond.

Your hair is super-straight.

A lank hairstyle makes your face look long and drawn. (Plus, if you have naturally wavy or curly hair, the hot tools required to achieve straightness leave your hair dry and dull.) If you have naturally fine, straight hair, ask your stylist for long layers and comb a lightweight mousse through damp hair from roots to ends before airdrying or blowdrying (avoid heavy styling creams or serums). If you blowdry, use a round brush to create soft curls at the ends of the hair; setting dry hair with Velcro rollers will also create softness and add volume to offset any drooping in the lower face.