We need to be fit to ski - the more performance we're looking for, the more athletic skiing becomes. At the higher levels, skiing is one of the most demanding sports, as we need not only strength, speed and agility but also the endurance required to put up with skiing potentially hard terrain all day.
Dryland training is very important in speeding up your progression, and while strength, conditioning and flexibility are important for sure, at the green level, balance is especially important.
We do not glide on one foot on a slippery surface often!
Simple balance drills you can do at home include buying a balance board and spending some time on it. Daily! Say reading the newspaper... err... iPad. Say on one foot. Say... couple minutes on each?
Jumping rope is a terribly effective thing to do to work on balance and conditioning for skiing!
Here are some ideas:
For blue/black levels, progress to:
More reading and references:
Here's a book on ski fitness: fit2ski.com/.
These two are good for mobility and strength:
Here's a good 30 min workout:
And here's a good pre-season 4 week program: