6 months to 2 years
Hold a soft, child-size toothbrush at a 45-degree angle; go over eating surfaces and the inside and outside of teeth in a circular motion, half on the gums, half on the teeth. Skip fluoridated paste for now; swallowing too much fluoride can discolor permanent teeth. Use plain water or a fluoride-free toothpaste, such as Orajel Toddler Training Toothpaste. If your water isn't fluoridated, ask your dentist about a supplement.
2 to 4 years
Continue to use water or fluoride-free paste until your child can spit into the sink. Then you can use a small amount of fluoridated toothpaste. Around age 4, when back molars are touching, start to floss. Wrap it in a "C" shape around each tooth and glide it gently.
4 and up
Let your child brush by herself with a soft brush, but follow up. Teach by letting her mimic you. An electric brush -- such as the Crest SpinBrush -- can help kids brush more easily and give them more gum stimulation. Whether she's using a manual or electric brush, she'll be ready to brush solo about the time she can tie her shoes.