Big Uncle gives good advice on getting acclimated. I live at 118' above sea level so I always get out there early in the week 3 or 4 days before the hunt. Take it easy for a day or two. Several years ago I had a bad case of altitude sickness so I take Dr prescribed Diamox now 2 days before I get there and 1 day after to help condition my body to run on lower oxygen levels. If you get one you will be shocked at how large they are. The meat is excellent.
If you can manage to work into the wind you often can smell them. They smell a lot like dairy cattle to me. The problem out there is the wind is always blowing and often changes so staying downwind is hard.