Be prepared for just about anything- 75 degrees and dry as popcorn, or 5 degrees, wind howling, snow two feet deep , etc.... or anything in between- sometimes in the same day.... be prepared to stay out all day so pack a lunch in your pack along with plenty of water and other necessities....
Altitude will be a big one so try to get there a day or two early to acclimate. Get to lower ground if someone gets a headache, light headed, or other signs of altitude sickness. It's nothing to mess around with...
Especially in new country, make sure each guy has a radio so you can stay in touch. A GPS is a great investment, but not totally necessary...
Biggest thing though is to have fun regardless of how good or bad the hunting is....
Bob