Replying to Teaching Someone To Ski

Searchbarred and didn't find all that much, plus hopefully other people can find this helpful as well, so whatever.

Basically this winter my girlfriend wants to learn how to ski (fuck yea) and I'll have to teach her. I've only taught people things in the park, never actually taught them how to ski. So my question is, any ski instructors out there or anyone else with experience, what are the most important things to teach? And are there any things to definitely not teach?

Thanks NS