Some 3-3 1/2 week-old cats already use a box. Do not use scoopable litter as they will probably eat it and it will get all stuck to their fur. Put them in the box and scratch their paws in it. Some get it right away and some don't. If they have any poo accidents outside the box, just pick it up with a tissue and put it in the box so they can smell it. An old baking pan is a good litter box, and they also sell "half" boxes almost everywhere. Another good box is for ferrets as one side is much lower than the others.

You will need to become super vigilant about picking up wrappers and throwing them away. If you put the trashcan in a cabinet, purchase those child safety locks and put it on the cabinet door. Rinse and wash all plates right after you're done. If you like to sit and chat around the dinner table, you'll have to do it without your dinner plates in front of you. You can put him in the other room while you eat. If you truly want to break him of this habit, you'll need to make sure that no human food is left out anywhere in your apartment. You can also purchase "canned air" from an office supply store and when he jumps up to scarf food off your plates, give him a blast of the air (but not in the face). It takes vigilance and dedication on your part and that of anyone else who lives with you, but your cat can be trained to leave your food alone.