The key to dressing properly is to layer your clothing. In cold or wet weather, three layers are ideal:
1.breathable wicking layer against your skin, to transport perspiration and other moisture away from your skin;
2.warming layer next, to absorb moisture and keep you warm;
3.waterproof and windproof layer on the outside.
Wear a synthetic layer closest to your skin to wick away moisture from perspiration. If you must hike in cotton T-shirts and shorts, carry other clothing to change into should the weather turn cold. Cotton soaks up moisture and doesn't dry readily, leaving its wearer wet and chilly when activity slows or when the wind picks up, as is often the case on a summit. When you stay cold and wet in adverse conditions, you can suffer hypothermia.
Hiking and other outdoor activities require a greater amount of energy than many people realize. Prior to a vigorous hike, enjoy a carbohydrate-rich meal. On the trail, munch high-energy snacks and drink water along the way. Don't wait until you feel hungry or thirsty. Sip water and nibble a handful of trail mix frequently. This will keep your energy level fairly constant. Trail mix (nuts, raisins and other dried fruit) is a good high-energy snack.
Carry plenty of water. You should consume from two to four quarts per day while hiking.
Hikers should always carry a day pack--even for short hikes-containing: