One can prevent Altitude sickness following ways –

• Follow the standard itinerary,
• Slow and Steady walk,
• Avoid the heavy bag pack,
• Deep breath time to time,
• Faster and deeper breath at higher altitude,
• Drink enough water and avoid the dehydration,
• Climb high and Sleep low,
• Don’t avoid the acclimatization day for above 4000m trek,
• Have a Diamox if no side effect,

Its quite wise to follow the above precautions. Then one can fully enjoy the trek.