1st Layer: Next to your skin the first layer should fit snugly, allow freedom of movement, and not absorb water. The most highly recommended garment for this is a polypropolene type top and bottoms. Silk or wool blend underwear is preferred by a few.
2nd Layer: The middle layer keeps you warm with insulation. Wool shirts, sweaters, and pile garments are ideal. This layer can be taken off and carried in the pack during strenuous activity or warmer weather. In extreme cold many people wear wool or pile pants as well.
3rd Layer: The outside layer needs to be weather proof and breathable. Goretex or treated nylon is the best. Hooded parkas or jackets are preferred by most. Pants of like material are also recommended.
Gloves: Insulated gloves or mittens with a nylon or leather covering are most common. Some people use wool, polypropolene, or pile liners. Some people like nylon over mitts. If the snow or weather is wet it is a good idea to bring an extra pair that has insulation as backup.
Socks: Poly propolene liners inside of wool socks are a good choice. Some prefer acrylic pile socks. Plush nylon socks may be all that is needed in warmer weather. An extra pair of dry socks in your pack will insure warm feet the entire trip.
Hats: Hats come in many designs and styles, they are essential for staying warm. Insulation is the most important consideration. If you don't have a hood on your coat a water proof hat is recommended. When it's windy covering the back of your neck with a scarf, turtle neck, or neck gaiter helps keep heat in.
Gaiters: Coated nylon, pack cloth, or Goretex gaiters are a must to keep socks dry and boots snow free.
Sun glasses: Sun glasses and goggles. When you need them you can't do without them!