Definetly arrive early and make sure that you are well rested. Like was said above, if you can sleep at altitude for at least one night and try for two before you start huffing it in the mountains it will help a lot. I have gotten altitude sickness once before because I over exerted myself at 11,000 feet. Sometimes it doesn' t take much.

Drink lots of water. When you think you have had enough drink some more.

Eat a lot of protene and carbs. The protene for long lasting energy and the carbs for quick energy.

Try to avoid excessive ammounts of caffine. If you are feeling a little bad it will only make it worse.

One more thing about over exertion, you can' t beat an elk in a race up a mountain.