Downhill skiing can be difficult and one of the most intimidating parts can be learning how to stop your forward motion.
Steps
Method 1
The Wedge
1
With your skis pointed in the direction of motion, start to spread your legs slightly, giving yourself some room between your skis.
2
Move your ankles and change your weight distribution to put pressure on the inside of your feet. This step allows the inside of your skis to start to grip the snow and form an edge.
3
Simultaneously with transitioning onto an edge, start to point your toes inward toward each other. This is what gives your skis a wedge shape.
Method 2
The Skid
1
Start with your skis both pointed roughly in the direction of motion.
2
Start to lean slightly to a side and put more weight on that side of the skis. For instance, if you want to lean left, then your left foot will put weight on the outside edge of your foot and your right foot will put weight on the inside edge of your foot. If you fall down, it'll be okay, since you were trying to stop anyway!
3
Lean slightly forward and press in with your heels by bending your knees. You might feel your legs press against the front of your boots. You can also kick out your heels to accelerate your transition. This should help turn your skis both parallel to the slope while keeping your motion in same direction you were headed. The edge of your skis and angle of the ski to the slope becomes crucial as it skids across the snow.