For those that live at lower elevations and flat land getting into shape is essential when hunting in the higher elevation west.
Steep ground and lower 02 levels at higher elevations will challenge those not used to the western mountain conditions. Going to your area early to get some acclimation will help, and practicing carrying heavy weights and getting legs into shape will prepare for the inevitable climbs and long hikes.
As per the article keeping well fed and hydrated is essential to maintaining energy during the long days.
Having a dedicated GPS unit (99.999% you won't have cell service), and good old fashioned hard-copy maps and a compass will help to read the terrain you'll be hunting in. Little screens don't always cut it.
Having a good med kit is also essential in case of an injury, as well as a sat phone/emergency personal locator beacon (aka PLB) in case you have a serious incident and need rescue.
My .02