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One mistake that most skiers do, once they're good enough to commit to the outside ski, is to forget about the inside ski. It ends up having a random amount of pressure, carving or just dragged along and, if lucky, parallel with the other one!
I find it then very important to focus on it, instead of the outside ski. I started telling my kids that Pinkie Leads the Way. They should start the turn with the little toe of the inside foot. And make sure the other foot follows. This was based on some corrective exercise i found on a website now forgotten.
Then, while paying more and more attention to the inside foot, you realize that it must lead the way completely - imagine needing to 'hook' the knee around a slalom gate -- you clearly have to push that knee sideways. So the inside leads not only with the pinkie carving in the snow but you will also push it forward and lead the other ski as you go through the turn. All this, after you pull it back to start the turn... the outside ski will generally follow, either willingly or not.
So, the sequence of the turn is, looking at the lower body:
That's where I am with my understanding of the turn right now, as far as using the inside foot. I will update this when it changes.
Update read this post Focusing on the Inside Ski for an update - note that I now consider it a mistake to push the inside ski forward early, as I had written in this post originally, it is important to pull the inside ski back instead. That doesn't change the perspective of pinkie leading the way though.
As we rarely discover genuinely new ideas these days, I later found out that there are some who built a sort of a movement around this idea, the PMTS. I just ordered two of their DVDs to see what they're on about and I will post an update here when I do.
Update I have received and watched the DVDs - see my review here: Anyone_can_be_an_expert_skier++ .
Lesson plans / drills: