How can I treat dry winter skin?

Moisturize. The only way to treat dry skin is to replenish the oils that are lost by moisturizing. The best time to moisturize is immediately after shower while your skin the damp.
Moisturizers. Moisturize body, hands, face with rich heavy creams after showering/bathing and before bed. Apply petrolatum products such as vaseline or aquaphor on the hands and feet and make the products penetrate deeper by occluding with cotton socks and gloves. This will also help the nails and cuticles. Avoid overwashing with hot water and harsh drying soaps.