I noticed recently that Warren Smith has an interesting page on skiing. He talks about how biomechanics and psychology are not always taken into account by ski teachers and can contribute to skiers remaining at an intermediate level for longer. He lists some typical but not exhaustive issues that can be solved with more awareness: giving tips on diagnosis and remedies.
One area of interest to me was unlocking the ankles. This year after a few years of skiing in my Nordica boots I finally wore them out and bought a new pair. The difference was immediately noticable: I was able to flex the ankles better. I was suffering from the first symptom on the list: not flexing my ankles enough (and only flexing my knees).
What is also really good about the page is that it gives exercises to build on your weaknesses.