This is a very good point. The best skiers don't always make the best brand reps. It probably helps to be approachable, friendly, and knowledgeable about the products sold by the company you are asking to sponsor you. At the end of the day, remember that the company is hooking you up because you help them sell products, not because you can throw dubs (though I imagine that can't hurt).
I have a buddy who is an awesome skier, but he gets great shop sponsorship not because of his skills, but because he drives a shit ton of business to the local shop who helps him out. When you're talking to people on your hill, send them to the shop you want to hook you up and tell them to let the guys there know you sent them. It's easier to ask for help when you've already given something in return.