A pregnant dog should have a whelping box, which is a secure place where she can birth her puppies. A whelping box helps the mother stay calm and it also keeps the puppies from getting lost or scattered. While large dogs need sturdy whelping boxes made of wood, smaller dogs can use sturdy cardboard boxes that can be easily discarded after the puppies are grown. Prepare your dog's whelping box two weeks before the due date to allow your dog to get used to it. She will enter it of her own accord and begin to birth the puppies.
Choose a cardboard box. The cardboard box should be large enough that your dog can lie comfortably while stretched on her side, but no larger. Ideally, the box should feel like a den to her, where she will feel enclosed and safe. The exact dimensions of the box will vary from dog to dog, but you can get a good idea of the size necessary by measuring your dog while she is lying down.
Use a box cutter to cut a rectangular notch in one side of the box. This will serve as the dog's entrance and exit. The notch should be deep enough that your pregnant dog will not drag her belly over the edge as she enters, but tall enough that the newborn pups cannot get out. The notch should be about double the width of the dog's body.
Line the interior of the box with plastic sheeting. This will make cleaning up much easier.
Cover the plastic with newspaper. After the dog has her puppies, you can clean up by throwing away the newspaper and replacing it with old towels.