Tips for staying warm while skiing

Every season is the same. I think I have all my gear ready when I go skiing, and then I discover omething's missing! Even though I've skied six times this season, the fourth day I hit the slopes was bitterly cold. I wasn't warm at all.

Then, I stopped to check my helmet and discovered the vents were wide-open. One hour later I was freezing round my torso; while I was riding the chairlift, I lifted the arms and found out that both opening were unzipped since the last time I skied with that jacket back in April! Will I ever learn?