only time I hiked at any altitude was Philmont, NM.
to prepare I just kept up my cross country workouts: a few days of sprints, and a few days of longer moderate runs 5/10K
One thing I havn't seen anyone mention is pay attention to your breathing, I find after a hard workout when others were panting if I stood up, arms over my head, deep breath in, hold it, then slowly exhale I would generally feel my heart slow down and breathing would be back to normal quicker and body as a whole would feel rejuvenated quicker
