I try not to spoil things or be spoiled anymore after my mother ruined part of the Half-Blood Prince for me.
She totally spoiled the big death in Half-Blood Prince for me and I still haven't forgiven her for it. I was reading the Half-Blood Prince review in the New York Times when I saw that they were planning on spoiling huge chunks of the book (because their reviewers are assholes) so I put it down and didn't finish it. My mother picks up the paper and starts reading and asks me if I read the review. I said I didn't finish it and the crazy lady says "Can you believe Dumbledore dies?" WHAT!?! I was so pissed off at her and I still bring it up from time to time when I discuss the ways she's ruined my life (joking, of course, love you Mom!). So now I don't spoil the endings to things - except I told the little girl that I watch that there is a half-vampire baby and tons of blood in the last Twilight book and she thought I was joking which led me to go "I only wish" - because of how upset I was over Dumbledore.