The first step in the horde Nagrand guide ask you to pick up the quest "Taking the Fight to Nagrand". The quest was not available to me and I found out that I needed to pick up "News from Nagrand" a quest in Spire of Arak. I had done Spire of Arak but I never got to pick up this quest.
Here is the quest needed:
http://www.wowhead.com/quest=36602/news-from-nagrand
I have not tested if this also applies to the alliance Nagrand guide.
Here is the quest needed:
http://www.wowhead.com/quest=36602/news-from-nagrand
I have not tested if this also applies to the alliance Nagrand guide.