Well, my experience might be different than others but for me, just getting in good riding shape and staying within your limits works for me. I live and mostly ride at 700 ft above sea level. I've done Ride the Rockies the past 4 years and have not noticed any issues with the climbs or altitude. We typically do passes 9000'-11,000'+. I fly the day before we start riding and hit the road early the next day. I just make sure I'm in pretty good riding shape and then watch my Heart Rate while riding. It is usually about 5% lower than the same rides wth the same effort around the house. I did seem to have some faint headaches while climbing Wolf Creek Pass this past year but that could have been from the local brewery the night before.