Along with ascending slowly and taking time to acclimatize, try the herb ginkgo biloba, used by the Chinese for more than 5,000 years. "Take 100 milligrams twice a day, starting a few days before your climb," says Dr. Peter Hackett, the president of the International Society of Mountain Medicine.

"We don't know why ginkgo helps, but in tests it reduces both the incidence and severity of AMS [acute mountain sickness]." The herb also increases peripheral blood flow, so your hands and feet may stay warmer.