Once you've placed all your weight on one ski, that ski tends to bend, which increases the effective side-cut or side-curve of the ski. Your bent ski begins to follow the arc of that deeper curve. And your job is simply to be a poised passenger, to ride that turning ski. At this point, everything depends on balance. On maintaining your balance right over that weighted ski.
Weight shift will start a modern turn, but only one-footed balance keeps it going. If you fall back onto both feet, you will lose the bend in your outside ski; your round arc will degenerate into a sideways skid. Of course, skidding isn't exactly a moral failure, but it's a lot more satisfying to shape a pure round arc. So how can you stay, perfectly balanced, over your outside ski?
First, practice one-footed balance at home before you get to the slopes. Lift one foot a few inches off the floor and observe how your body adjusts its balance. Chances are, you will spread your hands to the side, about waist level - like someone walking along a rail or a fence. This is exactly what you need to do to balance on one ski. Tiny adjustments of your outspread hands have a big effect on balance.
Notice how your torso shifts, gently and subtly over the foot you're standing on. This too is exactly what you'll do on skis. Do you own a pair of roller skates or in-line skates? Is there an ice skating rink near where you live? If so, I want to suggest skating as the single best preseason exercise to develop one-footed balance. And when you skate, stetch out each skating step as long and as far as possible - not great skating technique, but great skiing practice.
Then, when you finally start skiing this season, spend a few minutes on easy flat slopes, gliding straight, standing exclusively on one ski, then the other, for hundreds of feet at a time. It's far easier than you might think, but skiers seldom give themselves enough practice time on one foot... As you slide along on one ski, play with the other one, raise it, lower it, move it in and out in the air. Get comfortable with the notion, and the balance, of skiing on one foot. Finally, when you feel like turning, stay poised over your outside ski until you've arced around as far as you want. Change feet and repeat. It's that simple.
Lito Tejada-Flores is a ski writer, a ski instructor, and a skiing filmmaker. First and foremost, however, Lito is a skier and still in love with snow after all these years. His maverick book, Breakthrough On Skis, How to Get Out of the Intermediate Rut, has sold over 100,000 copies. And his "Breakthrough On Skis" videos are considered innovative ski-instruction milestones. Lito is the creator of an alternative on-line ski publication, www.BreakthroughOnSkis.com, which showcases his personal non-commercial writing about skiing.