Getting to 7-8k and staying a day, two or three before heading to the top is the best way.The best thing to do, I suspect is to arrive several days early and let your body start adjusting prior to long hikes. Even if you only get to 7-8,000 ft it would be a start.
I was going to say, have a fat gal set on your chest for three hours a day.Train while breathing through a straw
Best to try to find some mountains close to train
Its a whole new world when you are working your body above 8K. Buddy was cramping and not feeling well at all when we hiked from 8 to a 10K peak. Horses were not acclimated, and no way was I going to ride them up. The only real way is to get to that elevation or as close as you can and acclimate for as long as you can. In all seriousness go a week early if you can to acclimate. They have those training masks that help a little.Drew a tag for 12,000'. Live at sea level. Problem, major problem.
Losing weight is the easy part.
Joining a gym is the easy part.
Training for thin air, not sure what to do........................................................
I don't know, you might think about taking a few cans of "Boost Oxygen" and perhaps a bottle of Altitude Rx Oxyboost tablets I think no matter what you are going to need a little help in the end. Good Luck Cheers.I have a motel rented out at 8000' for 3 days before the hunt. Not quite 10,000', but it's the best I can do.