Hiking boots should be sturdy, with good traction and ankle support, and should be well broken in ahead of time. On less rigorous trails, some hikers prefer to wear athletic shoes instead. Wear thick wool socks, and bring an extra pair in case one gets wet. Rain gear is always a good idea, since the weather in most of the national parks can change drastically within moments. Drink at least 2 quarts of water per day, even more if you are hiking in hot weather.
Symptoms are chilliness and fatigue, followed by shivering and mental confusion.
The minute these signs are spotted, get the victim to shelter of some kind and wrap him or her in warm blankets or a sleeping bag. Ideally another member of the party should get in the sleeping bag with the victim for added warmth. If practical, it's best for both people to be unclothed, but if clothing remains on, it must be dry. High-energy food and hot drinks also aid recovery. To avoid hypothermia, always carry warm, dry clothing, avoid immersion or exposure to cold water or rain, and keep energy levels up by eating high-calorie foods like trail mix.