You shouldnt stretch (static) before skiing (or any other sports). Instead do a normal warm-up and ballistic stretching. Ballistic stretching uses the momentum of a moving body or a limb in an
attempt to force it beyond its normal range of motion.
For better flexibilty you should look into PNF stretching. This should be treated like a strength execise and not something you do after sports.
This kind of stretching involves the patient to fire the tight muscle
isometrically against resistance for roughly 20 seconds.
Then, the patient relaxes for roughly 5 seconds,
and then applies a stretch at the newly found end range. This technique
utilizes the
golgi tendon organ, which relaxes a muscle after a sustained contraction has been applied to it for longer than 6 seconds.
My advice would be to do your own research on this topic.
sources:
http://www.marykaa.com/fitness/PNF/pnf1.htm
http://www.tmuscle.com/free_online_article/sports_body_training_performance_interviews/the_stretching_roundtable_i