Train harder than you think you need to, the altitude will hurt you. Prior to my trip out in October I was hiking 4-5 miles with a 60 lb pack at least 3 times a week. And I tried to fit in a 8-10 miler each week if time allowed. I thought I was in pretty good shape, as soon as I started going up hill at 9000 feet I felt like a little bitch.

Be prepared for some crazy weather. Went from low in the 30's highs in the 60's to below 0 lows and single digit highs overnight.

Clothing wise get a good layering system. even at -6, when moving, I was comfortable with merino base layer, wool shirt, down vest, good gloves and beanie. I carried a heavier jacket and a light sleeping bag to use when stopping to glass, eat, etc. Gaiters are for the snow or dew.

Newberg has a good video series on e-scouting.