Avoiding or minimising altitude sickness?

The best thing you can do is acclimatization. This means you should adjust your body gradually to the height. This can be done for example by increasing the height you're staying from day to day. Another very important fact that is widely used by mountaineers is that you should always sleeps some meters below the highest point of the day. So for example you reach the height of 4000 meter where you plan to spend the night. Before going to sleep you should if possible gain another 200 - 300 meters, spend some time there, then go down and sleep at 4000 meters.

A lot of mountaineers also use Acetazolamid (Diamox) which can be taken preventive. But it's use is discussed controversialy because it has a lot of side effects.

Additionally to that you should drink a lot, but no alcohol and you should also take care of you're nutrition. It is very important that you force yourself do not use a lot of power. (this is particularly important when climbing a high mountain. You have to force yourself to walk slowly enough). If you feel slight symptoms it isn't necessary to do anything, but if it gets worse you should go down to lower altitudes as soon as possible. If it is really bad, you should immediately seek medical help, because it can kill you.

First of all DON'T listen to tour operators. I made this mistake when I went to San Pedro di Atacama (Chile). On the first day I bought a tour to >6000 m. I suffered a severe form of altitude sickness. Afterwards I could judge on the pictures taken that the scenery was breathtaking. While at location I only felt miserable. I needed 2 days to recover, which was a waste of time. I did miss quite some other things to do while there. While there I talked to other travelers and they told me that it was plain stupidity to go on the advice of tour operators. They don't think in terms of returning customers. As usual there are good ones that suffer from the bad ones here, but since then I prefer to listen to peers.

In the same week I also went to the geysers which also were at high altitude. Then I took the advise to drink liters of "mate di coca" which is sold at every bar there. Don't worry, although this tea is made from the same ground material as cocaine, you need tons of these leaves, to make cocaine. It could also be, that my body got adjusted to the altitude in the days after the first altitude sickness, but I enjoyed my trip to geysers to the fullest.

I think Mark already mentioned most things you can do in his question.

There is also some medication you can try. In Bolivia this stuff was pretty cheap (as was most other medication) and I assume it is readily available in places where it is needed.

I also like to emphasise his point about the randomness of mountain sickness, just because you are fine in one place, doesn't mean you are safe up to that altitude.

I went up to 5500 meters and spent months in places over 3500 meters without any problems, but then one time at about 4200m I experienced some symptoms. In that case the medication helped.

Also I met locals in Ecuador who lived all their life over 3000m and got pretty sick by going up to 4500m.

There is plenty of high altitude to be had in the great indoors as well as the great outdoors. When I taught a course in Colorado Springs, I was astonished at how thirsty I was. I always have a bottle or two of juice or water a day when teaching (standing and talking is actually thirsty work), but I drank both of them by morning coffee break. I replaced them, and drank both by lunch, and so on. Eventually I commented to my students how I could not understand why I was so thirsty. They said they assumed I had been told to drink that much, and that it was in fact the best way to prevent altitude sickness. I didn't have any ill effects (other than raising some eyebrows when I submitted my expenses) and would recommend drinking many litres a day more liquid than you would at your own altitude.

Since no one has said the obvious yet, I'll go ahead. The best way to avoid or minimize altitude sickness is to avoid high altitudes. Thank you, I'm here all week.

I did actually want to add one other traveler-related piece of advice on this topic. Don't go scuba diving within the unrecommended time before flying on a plane. Here is a link to PADI's recommendations: http://www.padi.com/rdp/erdp/General_Rules_using_the_eRDP.htm PADI is the world's foremost organization on scuba diving. Although I have heard some dive instructors make more conservative (longer time) recommendations. Certainly the argument is made here http://answers.yahoo.com/question/index?qid=20071130220055AAIdoa9 that this general recommendation is just that: general. Better advice might be to follow your particular guide's advice and always go with a reputable guide if you're not comfortable on your own. If you are comfortable on your own, you shouldn't need this advice! ;) Airplanes usually pressurize the cabin equal to the atmospheric pressure at 8,000 ft. http://www.who.int/ith/mode_of_travel/cab/en/

And to bolster/undermine what other have said:

I live at 5,000 ft and travel and stay at altitudes above 8,000 ft every 6 mos or so. Not enough to get "permanently" acclimated to the higher altitude though. My relatives from about 1,000 ft come to visit here (5,000 ft) and can definitely get altitude sickness. DRINK WATER. I've gotten to the point where I can tell I'm getting a high-altitude headache because I haven't had enough water at the higher altitude. I don't agree with those who say it can be bad for you. It is really hard to over-hydrate. It happens but so, so rarely, you'd have to be really trying to do it. The thirst mechanism is very weak. Usually if you've waited to drink long enough to be thirsty, you've waited too long.

Diamox made me pee a lot, but worked for me climbing Mt. Kilimanjaro.