Learn to use a mouth call for mews. I blind-called in a herd of cows/calves on opening day a couple years ago while taking a break hiking back to camp along a finger ridge. Two big cows stayed there for a while looking around, both with trees blocking the goodies. While this was going on I had others hanging around across a thick shallow draw with no shots. Most exciting time ever in the mountains other than another time I had a bull raking trees below me and grunting. Never did see him, but the next day I climbed down and saw the trees he tore up...
It's addicting to say the least. Here's a few pics to get ya pumped for the trip.
Take your time to get used to the elevation and like others have said, drink A LOT of water.
Another thing, before making a fire be sure there's no fire ban in effect by the county OR Forest Service for where you hunt. Also, check out the Colorado COW website, it has maps and info to keep you entertained for a while.
Good luck! I can't wait to go back out there.