Balance is the key to cross country skiing. It is crucial to both skating and classic skiing and a tried and true drill is the ‘scooter’. Use this early in the season when balance is off. To do the scooter put the foot with a ski on it in the track and push down and back with the "skiless" foot just outside the track (that way you don’t get foot prints in the track). Balance on the gliding ski for as long as possible. Start with small pushes and then as balance improves, push harder or try the drill down a slight downhill. It really helps to lean forward to counter balance the extending foot. This is a great drill for beginners but racers will also benefit. To add a challenge—add a hop with the "skiless" foot.
Skate: Getting Hip
Bringing your hips forward is an important skill for improving your diagonal stride. Leaving your hips back is a common problem and makes it difficult to shift your weight adequately as well to prepare for the next stride. So try this exercise - start by holding your poles across your bottom. Then stride forward pulling your hips forward with your poles as you complete the stride. This helps you stand taller and prepares you for next, bringing your recovery leg actively forward. Be careful at first since this exercise is abit unnerving. At first- you feel as if you are going to fall flat on your face. But once you get use to it the drill will work wonders for your technique.