That orange oil goo remover works a treat, just be careful when using it on light coloured cardboard because it can soak in an cause a faint stain.
Another thing you can do is use the same price sticker once removed to clean up any sticky residue which may remain by dabbing the area. It's a bit hard to explain, it's like touching the sticky areas with the same sticker breifly and then pull it off again, most of the time that's enough to remove what remains.
Of course the sooner you get the stickers off the better, before the glue goes hard and makes it near impossible to remove.