Agree with lots of core, glutes, and body weight workouts. If you're doing weight training and you can't safely, without breaking form, do 10-15reps, you're using too much weight. Foam rolling and dynamic-stretching as a warmup before training/skiing and foam rolling and static-stretching afterwards as a cool-down. Very much recommend the high-density foam roller, it can be a little uncomfortable, but the benefits greatly outweigh the discomfort. Good luck, stay stoked!