I don't have any stories about myself, not because I wasn't ever ignorant -- I'm sure there are plenty of derp moments from me in classic -- but I just can't remember them. So instead I will tell two pertaining to people who began playing WoW because of me:
• I had a friend who didn't realise you could shift+click stacks of things to purchase/sell/trade/buy in partial quantities... until Wrath. He began playing in late-classic!
• My father who didn't realise talent points even existed until his character level 40+ (nothing in the game tells you!) and might have gone even longer if I hadn't noticed.
I feel responsible for them, as if they were my own mistakes, since I was the one introducing them to and teaching them the game, and these are not things you really learn without reading somewhere or having someone tell you.