It is just in the world state. I won't go into the actual choices, because that's a different question and has been answered here.
With a little of the beginning plot, you can see where the previous games make their mark on Inquisition. While it being minor spoilers, read carefully.
With the assistance of Hawke (the protagonist of Dragon Age II), the Inquisitor investigates the disappearance of the Grey Wardens, discovering that they were being manipulated by Corypheus into raising a demon army. Hawke and the Inquisitor are assisted by a Grey Warden character from the previous games in the series, who may be either Alistair, Loghain, or Stroud, depending on choices made in previous games.