one word! ibuprofen (it increases oxygen flow). i lived in a cabin @ 7,750 ft. for two years w/o running water, electricity, or heat while in durango, co.. while i wouldn't do it again, it was one h#ll of a learning experience.
p.s. i've had climbing/spelunking experiences that would make your skin crawl. i watch videos of special forces training in rock climbing and, literally, laugh my @ss off.
i was never world class, but, i've seen grown men drawn to tears facing adversity.
if i were in my 20's again, i would probably be sponsored by red bull. ;)
Another word: Gingko Biloba*. There is anecdotal evidence that taking it weeks/months prior to your ascent allows your red blood cells to carry just a little bit more oxygen than they normally would. That little bit more is supposed to be a big bonus at high altitude.