The key to preventing altitude sickness is to acclimatize properly. In high altitude areas, you should not gain more than 600-800 m of altitude. We advise you to take things easy and not to trek in a hurry.
Regular hydration of at least 5 liters of water a day is a must. Diamox (acetazolamide) is not recommended. Diamox simply tricks the body into breathing faster (by increasing the blood Ph slightly) and in fact avoids symptoms. Acclimatization is the only treatment for high altitude sickness. Take medication only if it is recommended by your doctor.