From this post in rec.backcountry, it looks like the best precaution for altitude sickness is to have a big head or being taking Ginkgo biloba. The study also noted that the classic "over hydration" has no effect!
From: Fwank Lichtenklitz (email@example.com)
Subject: The Latest Re: High Altitude Illness
Newsgroups: rec.backcountry, rec.climbing
View this article only
Date: 2001-10-03 21:56:35 PST
High Altitude Illness, Peter Hackett, MD and Robert C. Roach, Ph.D.
New England Journal of Medicine, July 12, 2001
1991 Colorado study: acute mountain sickness (AMS) in 22% @ 7000-9000ft;
42% @ 10,000ft. Risk factors include previous bouts of AMS, residence
below 2800ft, exertion, and preexisting cardiopulmonary conditions.
Persons over 50 years of age are somewhat less susceptible to AMS
whereas children are about as susceptible as adults. Women are less
susceptible than men to HAPE (High Altitude Pulmonary Edema) but equally
prone to AMS. Physical fitness is not protective against high-altitude
sickness. Genetic factors and the environment probably explain varying
individual susceptibilities. Descent of only 1500 to 3000ft usually
leads to resolution of AMS (HACE--high altitude cerebral edema--may
require greater descent).
New evidence suggests that ALL people have swelling of the brain at high
altitudes. One hypothesis is that those with a higher cerebrospinal
fluid volume to brain volume experience AMS less often, since they have
more skull space with which to accommodate brain swelling.
400mg to 600mg of ibuprofen decreased or resolved high-altitude headache.
Gradual ascent is still the best strategy for AMS avoidance.
In two controlled trials, Ginkgo biloba (80mg-120mg orally
twice daily) prevented AMS during a gradual ascent to 15,000ft and was
50% effective in an abrupt ascent to 12,500ft. Prophylactic aspirin
(325mg every four hours totaling three doses) reduced the incidence of
headache from 50% to 7%.
The notion that overhydration prevents AMS has no scientific basis. (!)