High speeds and challenging terrain require refined technique.
Downhill and GS racers skip the pole plant altogether. You can do the same when you are cruising. The pole only gets in your way. Keep your head up and your hands ready (A). Cross over with your upper body to change edges, and let your shoulders "reverse" (counter) slightly (B). Let your feet flow out from under you (C), and then level your shoulders and bring them square with where you're headed (D). Now you're going for it!
Once you plant the pole and begin your pole swing for the new turn (A), drive your outside hand down, toward your outside foot (B). This increases pressure on your outside ski, and helps ensure that your shoulders stay level.
When it's steep, face downhill and reach way down the fall line with your pole (A). A big reach does two things: It pulls you across the skis, away from the hill and into the turn (B), and it guarantees you won't trip over your pole when your skis slip sideways, as they will on steep terrain.