Put him on a down-stay. If he doesn't know this already, take him to obedience class, or teach him yourself. If at first he keeps getting up on a down-stay, put a house leash on him and tie the leash to a weight or a piece of furniture. Soon he should be able to hold his stays. Also, it helps to do a long down-stay (30 minutes or more) per day. This will teach your dog to relax and settle down, while you go about your business.