Goo gone is probably the best way to remove stickers. Bubbles are pretty easy, cardbacks are a little tougher. You should practice on a cheap figure first before proceeding to that carded yackface.
typically a few drops of goo gone on a sticker and it will remove easily. usually there is a little residue left over, and slight rubbing should remove it, however, rub too long, let the goo gone sink in too long then rubbing, etc. and you could end up taking a little of the paint off the cardback.
Still, it usually works pretty darn good.