The most effective acclimatisation takes place with reasonable, but not excessive, levels of respiration. So whilst lying in your sleeping bag on a rest day is not good, neither is charging about trying to gain height too quickly. The ideal is what I call ‘active pottering!’
Make sure that your expedition itinerary has sufficient time for rest days and a slow rate of ascent. Do this and you should be relaxed and confident that you will acclimatise well and may even enjoy your time spent high. Anxiety about your acclimatisation will not help, so be aware, but not ‘over-aware’, of any symptoms of AMS you may encounter.
Being relaxed, patient and adopting the slow pace of expedition life will also help. Take some good books and an MP3 player so you don’t lose the will to be hanging about base camp or staring at the top of your stormbound tent. Make the effort to get to know the local staff team with your expedition, (Sherpas, cooks and porters) and you will be unlocking the door to hours of good banter and fascinating cultural exchange.