As a private instructor, I believe that nothing beats a day on the slopes working one on one with an expert, but a lot can be learned and reinforced with a great instructional video.
Elate Media, who also also sells the Ski School app for on-the-slope instruction, has a series of well-produced videos worth watching. Their 2 to 5 minute videos span from basic to advanced topics. Each topic is broken down to cover a specific task or technique. Here are a few of my favorites available on YouTube that address some of the most important principles of alpine skiing.
Edging is one of the "breakthrough" skills that takes an intermediate skier to advanced, giving the skier a sense of confidence and control.
Carving Your Turns
When you learn to carve your skis without skidding, the grace of your form and efficiency of style makes you one of the beautiful skiers on the slopes. Your skis, the stored potential energy, and the forces of gravity start to work for you, rather than you working against the mountains.
As always, if you have any questions or would like tips on making the most of a ski vacation in Colorado, don't hesitate to email me at firstname.lastname@example.org - enjoy!