How exactly do you interpret the Long Canyon Card?
Instead of setting up along the long end of the table, you set up along the narrow side—that is to say, instead of the table being 6x3, think of it as being 3x6. You can't put any of your units at the very back of the table, either; they all have to be at least range 3 away from the deep edge, and can be up to range 5 in from that line. (You can bury terrain you don't want in the game along the back side, though.)
Similarly, can anyone give a more detailed explanation of the instructions for Set Up on the Hunter's Quarry card?
It's a fairly basic setup. You put out three objective tokens. They can't be near your starting area (at least range 3 away), other tokens already placed (range 3 again), or real close to the edge of the board or any terrain (at least range 1 away from those). They can be inside your opponent's deployment zone, but that's likely to give points to your opponent.
The biggest difference between this setup and other similar ones is that after each turn, the objective tokens start moving around.