In the morning, just hang out by the ticket booth and look for people obviously from out of town, making furtive glances and not wearing any ski gear (it could also be some one who works there looking to sell as they get these things for tips sometimes). If it is around lunch time, just approach people heading to their cars and packing up for the day. If it is at the end of the day see who's in the first aid room waiting for transport.
Works everytime; from Colorado to BC so far...
It's against the law of course. But it's a stupid law