As a fellow flatlander (middle TN) with a few western, mountain hunts under my belt, I would say that all the above advice is great.
It's greater if you're basically a fit, active guy.
I'm not that. I'm a tubby cubby that drinks way to much, eats too much & would rather have a tooth pulled than go to a gym.
I try to work out for the 3 months before I go west, but don't always succeed.
The one piece of advice I would give, is no matter what anyone here does, don't compare yourselves to them. They live up there. They work, daily at altitude. We don't. Go slow. Don't over exert yourself.
Train add much as you can, however you can, but please...Don't try to be one of these western guys.
There's no shame in not being able to climb from 9k to 12k in 4 miles, in 4 hours.
My first shot at Colorado, it took me 8 hours to climb 3 thousand feet. By mile 3 I literally hiked 50yds, then had to stop & rest for 10 minutes. Admittedly, I was carrying close to 70lb, but with even half that, I don't think I couldn't shaved more than an hour.
You know what? I still had a fantastic time!
Getting to understand exactly HOW the lack of oxygen affects you is the biggest hurdle, I think. (It's like breathing through a drinking straw....) My first trip to Wyoming nearly killed me. My second trip, I'd actually gained 30lb, but because I knew what it felt like, was much easier.
If you're struggling, stop. Breathe. Drink lots. Take altitude Diamox & eat your way through a pack of Rolaids a day while you're there. You'll probably need a sleep aid for the first couple of nights too. Diamox will have to be prescribed & is expensive, but it's totally totally worth getting.
