When landing switch, make sure you spot the landing. When you touch the ground (and the moment before) you should be looking at a point appr. 10 ft up the hill. If you stare at the ground beneath your feet like beginners tend to do you'll land front seat and/or wash out.
Don't bend your knees too much, focus on keeping skis parallel (as opposed to snow ploughing) and flex your core muscles, and you'll be landing like Tom Wallisch in no time.