"Many of my patients are diligent about using sunscreen on their faces, but forget about protecting their hands," says Wu. "Even if it's cold outside, the sun can be bright, and UV rays can make brown spots worse."

To avoid brown spots (and keep more from appearing), always wear sunscreen on the backs of your hands. Use a daily lotion with SPF 30-50, with broad-spectrum UVA and UVB protection. Many hand creams now come with built-in sunscreen. We like Supergoop Forever Young Hand Cream SPF 40.

Wu says you can also go vintage by keeping a pair of driving gloves in your car. Alternately, hold the steering wheel in the six o'clock position with your palms up.

So, you haven't been diligent with your sun protection. Luckily, there are some ways to treat brown spots -- especially if you start early. "Newer, light brown spots may respond to lightening and brightening creams with ingredients such as soy, arbutin, and vitamin C, or prescription retinoid and hydroquinone," Wu says.

Try a serum like Mario Badescu Vitamin C Serum, or a moisturizing hand lotion like Ahava Age Perfecting Hand Cream (it contains a blend of dead sea minerals and nourishing algae).

If you're dealing with dark spots that have been around longer than a year, you'll need to make an appointment with your dermatologist. Your doctor can treat spots with a laser, like PicoSure (the first picosecond laser to be FDA-cleared to treat benign pigmented lesions), or a chemical peel.

Are your brown spots lumpy, as well? "For raised brown spots, I sometimes treat with liquid nitrogen, which freezes them off," says Wu.

If you don't take care of your nails, you basically seal their fate: dry, cracked, and ridged, which drastically ages the appearance of your hands.

Nails also begin to show vertical stripes, which Jaliman calls the "wrinkles" of the nails. No thank you.

Arm yourself with a cuticle oil to keep your nail beds in tiptop condition. And, we hate to say it, but it is time to toss your nail-staining dark polish.

Wu says to avoid acetone nail polish remover at all costs. Try RGB Nail Polish Remover which, in addition to coming in convenient and portable packaging, is soy-based and won't strip your nails.

The best thing you can do is to file down your nails where they've split or cracked, and buff out any ridges, Wu advises. Bonus: buffing also gets rid of discoloration.

And switching from darker polish to a lighter one does more than just prevent stains -- Wu says that lighter polish colors make ridges look less noticeable. She also recommends taking biotin, a type of vitamin B that can help nails grow.