Read your manual. Pick up the recommended powder and correct caliber bullets. My father in law only shoots with sabots, although I used to shoot only a lead projectile. A bullet starter. Cleaning supplies. Whatever caps it takes... something to hold a couple extra charges of powder and bullets and you should be good to go. I've probably forgotten something, but I'm sure someone else can jump in.
Shoot some target practice before going and don't clean between shots... most likely you won't clean in the field if you miss your deer.
