The base technique of the classic track: push off from the kick zone, then glide on one ski. Arm and leg work diagonally — right leg forward, left arm forward.
The diagonal stride is the base technique of the classic track — get it right and every other classic technique builds on it. The typical beginner mistake is skiing it like fast walking: short, stomping steps with no glide phase, plus an upper body swinging from side to side. Both take pressure off the kick zone, and that pressure is exactly what creates grip. So practise without poles first: push off, shift your weight fully onto the other ski and let it run as long as it will. Your upper body tips forward, never sideways. What often gets missed: without a full weight shift even the best kick wax won't hold — slipping skis are more often a technique problem than a wax problem.