As soon as you see the first tooth coming through, brush it! They make special toothbrushes for baby’s that are small and idea for cleaning little mouths. For ages two and below, use a rice grain sized amount of toothpaste. Ages 2-5, use a pea-sized amount of toothpaste. If your child has no teeth, use a damp washcloth to clean their gums. During bath time is a great time.