I picked up the core set yesterday, and I'm thinking about getting the deluxe expansion next, but before I go getting any extra cards, I have a bit of a question about stories.

The core set comes with 10 stories, the expansion another 10, and I feel like I've seen a reference to one of the monthly packs which had quite a few more.

Once you get more than 10 different stories in your possession, how do you decide which ones to use? obviously players build their own decks for personal advantage, but I feel like being selective with stories could benefit one player a lot more than another- do you each pick half? just do it randomly, or is there another approach?

If you are playing "official" games - something sanctioned by Fantasy Flight, then the story deck is defined by the Tournament document. Currently it is the 12 stories in Shifting Sands.

If you are playing for fun - do whatever you'd like. One of my guys likes to bring all the stories he owns into 1 big deck, for example.