Clothing for cross country skiing is versatile. You can use tights and windbreakers made for skiing, bicycling, or jogging. Ski shops carry stylish functional materials, but you can supplement specialized garments by raiding your closet for sweaters, long johns, hats, and mittens.
Conventional cold weather clothing like bulky parkas isn't suited to cross country skiing, as it constricts movement and generates excessive body heat. The trick is to retain warmth while allowing perspiration to evaporate. You get this by layering clothing to adjust heat loss to pace, terrain, temperature, and wind speed.
Wearing several light articles of clothing - for instance, polypropylene or similar underwear and synthetic fleece overpants plus windpants, with a wool or fleece zip sweater and a wind-resistant jacket - allows you to trap warm air in pockets of space. In most conditions, wear just one or two insulating layers, depending on the weather and the kind of skiing.
A lot of synthetic fabrics have the ability to wick moisture away from the skin and onto the next layer. In turn, the middle insulating layer should be quick-drying or wicking as well, so moisture ends up as close to the outside as possible. (Moisture and cold air aren't a happy mixture.) If underclothes are wet and your skin is clammy, there's an increased chance of hypothermia (a lowering of the body's core temperature). Cotton acts like a moisture sponge and accelerates chilling, so jeans definitely aren't recommended.
Aside from buying warm, comfortable, breathable boots, the best thing for your feet is layering, too. Try wearing thin polypropylene liners under a pair of wool or wool-blend socks. If your toes are susceptible to cold, resist the temptation to put on too many socks - you'll only restrict circulation, making your feet colder.
Mittens are best if you're prone to cold hands, since they allow fingers to share body heat. Gloves are better for precise ski pole control. For chilly weather, look for gloves with leather/synthetic palms, a long gauntlet at the wrist, and a light lining; in warmer conditions, critters a lot like handball gloves can be fine. Don't use too heavy a pair or they'll be sweat-soaked in the first kilometer.
This information is excerpted from Cross-Country Ski Vacations: A Guide to the Best Resorts, Lodges, and Groomed Trails in North America by Jonathan Wiesel. To order, visit amazon.com.