Do I need to do anything special to tonight's risotto so it makes good risotto cakes/balls tomorrow?
No, just cool it down and refrigerate it. One of the best things about risotto is cakes the next day.
You can also form the risotto into balls, stuff a piece of prosciutto or mozzarella in each, coat them in bread crumbs and deep fry. These would be arancini or suppli depending on where in Southern Italy you are.