I don't fully know yet but tried to get an inspiration. When the New York Fashion week took place for Aw 2013 Most models had their hair down low, not exactly wavy or straight. Another thing that you could notice was a low ponytail with bits of your hair just hanging out at the front . And mostly a side-part in your hair.
So when I went on the website of Zara it was just brilliant as it had every detail of what I had seen in the fashion week already there.
Their hair is 'The Hair' for Fall.