We're going skiing soon and I have no idea how to dress. I have ski pants and a ski jacket, the jacket has a zip out fleece. But what do I wear underneath? Do I need some sort of base-layer? Leggings or tights? Sports bra? Are ski socks usually thick or thin? I have zero athletic clothes, help!

I'm a complete novice and plan on taking lessons. I get warm easily, so I'm more worried about being hot and sweaty rather than cold. But I don't know how intense the lessons will be, so maybe I don't need to worry about this? Also, I plan on buying my own helmet, any specific features I should be looking for?

What do you seasoned skiers wear? Any other suggestions or advice?