Before you head to the mountains it is a good, well really great idea to do a little conditioning before you hit the slopes. Being aerobically fit decreases your chance for body soreness due to muscle fatigue and injury. But you have got to add a little anaerobic work into the mix, since skiing and boarding both require short, quick bursts of energy.
So you need to add sprints to your regular work out routine - you can do this on a run or on a bike. Try to add some 2 minute intervals of sprints, taking a short break after the sprint (don't completely stop, but slow it down a bit).
See you on the slopes.