Avoid Altitude Sickness
1) When doing any type of cardio vascular training (after you're at a decent fitness level), keep a fighters mouth piece in at all times. This is a very cheap and affective way to simulate the lack of oxygen you will be facing when at altitudes of 11,500 feet or higher (this is where the goats live). I know this seems a little overboard, but you will be thanking yourself for doing it when you're on the side of the mountain. Using a snorkel works even better, but you get some funny looks when running on the treadmill.
2) Take a supplement like Wilderness Athlete Altitude Advantage. This will put you several steps up the ladder before you even get above sea level.
3) If you're a flatlander, climb as many stairs as you possibly can. This is the closest thing your going to find to a 45 degree slope. As you gain ground on your cardio level, put on a backpack and add weight accordingly.
4) Drink as much water as you can before, during and after your hunt. This will help out greatly with your acclamation period and lesson the chances of altitude sickness and headaches.
5) Add supplements to your water like Wilderness Athlete Hydrate and Recover during your hunt. This will help replenish your electrolytes quicker and keep you from getting that sluggish feeling.