This is a very interesting discussion, I'm curious to see how it will go.
I agree with others that skidding and skiing away from the fall line are the two primary ways to control speed, often done in combination.
I would like to suggest that skiing the slow line fast is rather self explanatory. Finish your turns. Enough said. I do not particularly think that skiing the slow line fast is the more difficult of the two methods, but often its overlooked by some, so yes its a good one to learn, very early on. Turn out of the fall line.
From where I am standing, refined use of skidding is the more advanced skill to talk about and the true mark of expert skiing.
I usually see two kinds of skiers: I see the kinds that can easily carve arcs and ski the slow line fast, etc. But sophisticated and subtle use of refined skidding seems to be kind of a lost art form since the advent of shaped skis. So the other type of skier I see are the ones that seem to ski Z shaped turns with a lot of skidding during the end of the turn, which is NOT high level skiing.
A truly high level skier can use much more elegant and controlled skidding, which results in S shaped turns, with speed controlled throughout the turn. Controlling the edge angle, pressure and steering angle "just right", while also going through the proper movements to carve and steer the turns, is the mark of someone that can really control their skis, go as fast or as slow as they want, on any line they want. (well within some reason). I'm not talking about pivoting, wanted or unwanted. I'm talking about steering.
Mastering the use of skidded steering, is a much more complicated subject and one worth talking about.
Edited by borntoski683 - 11/2/11 at 5:10am