You may notice that your breathing is faster or deeper and you may feel short of breath, especially when you exercise. This is the body's first and most effective response to altitude. Once you arrive, take it easy for the first day of two. Reduce consumption of alcohol, caffeine and salty foods. Drink more water than usual.
Altitude illness feels very much like flu or a hangover, but is much more serious.
Do not push. The sun has more power in the thin air, and a bad sunburn can spoil your stay. No matter how tanned you may be, use a protective cream. Sunburn of the eyes is a real danger, even on foggy or cloudy days. Wear sunglasses or goggles with ultraviolet protection.