I knew that there was something called "Red Wedding" in A Storm of Swords and that Robb was "briefly" married with Jeyne Westerling (thank you wiki). However, i thought that Jeyne would die and that the Red Wedding was Joffrey's wedding, so it did no harm.
I also got spoiled about Arya going blind, about Littlefinger killing Lysa, about Ygritte becoming a lover to Jon Snow (but that was pretty obvious from the beginning), about Arya not being killed by the Hound (after the RW he gave her an axe blow), about Bran and Rickon surviving Theon and about Davos not being killed by Manderly.
Sometimes even knowing that someone has a POV is a spoiler, because you know then that the character is not dead. For example, it was a tense reading for me the Jon chapter in A Storm of Swords where he and a few black brothers defend Castle Black against Magnar. Reading this shortly after the RW I was very worried about Jon's life. If I had known that Jon is a major A Dance with Dragons character (and worth many theories about his origins) the fight would have been much less enjoyable. That was the case with Bran, Arya and Davos for me.
Edited by clydas, 07 October 2012 - 01:31 PM.