I could give a carefully worded unsolicited advice to a random guy on the hill but I wouldn't dare approach a woman. Maybe just to ask if she's ok. But never to tell her what to do. Self-preservation instinct.
Haha. I usually start off with a basic conversation, regardless of gender.
"Hey, how's it going? how long you been snowboarding for?" .. but then again I usually ramble on with anyone on the hill. If they seem content to just keep to themselves, I ride off no harm done.
It would be pretty hilarious to skate over to someone and start telling them to get their weight on the front leg or something ... probably wouldn't go over so well.