If another skier or snowboarder hits you and injures you, always call the ski patrol immediately. Take care of yourself. But it is also very important that the other skier or snowboarder not leave the scene. At least ask them their name and where they are from.
You should remain calm, which is often difficult in these circumstances. But if you or one of your friends or family members are hurt, it is of utmost importance to be able to identify the person who caused the injury so that you can actually pursue a claim against them.
Document, document, document. These cases are just like any other case. You want to preserve evidence, document the conditions, gather witness statements from as many witnesses as possible, and do everything you can to preserve evidence of what actually happened and what the situation was that actually caused your injury.