First I pick a highly contrasting bag and open it up so I'm looking at the front of the bag.
I don't open up the bag all the way because it saves space and works just as well.
Then I drape the scarf around the bag as though the top of the bag with the opening was my shoulders.
Then I take one end, flip it across the front of the bag and let the end hang over the back. Again, just like you would do if you were flipping it over your shoulder. I take the end that is still dangling in the front and spread it across the bottom of the bag so it "pools".
For the final, and most important touch, I prop the photo card on the scarf. You can see how much more striking the scarf looks with the contrasting bag and the photo card that is color-coordinated with the scarf. Just waiting to catch the customer's eye.