Perhaps the most important ingredient for a fun and safe cross-country skiing outing is clothing. Layering is putting on many different layers of clothing as opposed to one large parka or one thick sweater. A sweater of wool or synthetic pile makes an ideal middle layer of clothing. Anoraks jackets and shells that are waterproof and breatheable work great for outerwear.
Polypropylene pull-on pants, bibs or rain pants are fine.
Be sure that you have something warm under the pants if they are not lined. The new waterproof,breatheable materials such as Gore-Tex, Ultrex, etc. are excellent for ski clothing, but can be expensive. You can still wear wool clothing as wool wicks well, but it is not waterproof. Wool clothing can be found at clothing surplus and second-hand stores at a reasonable cost. Cotton Clothing such as Jeans and Sweat-shirts are inappropriate for skiing.