Have your kids drink lots of water! If you buy bottled water, make sure it contains fluoride.
There is a lot of sugar in foods/drinks children enjoy that can cause tooth decay. For example, cereal bars, boxed snacks, chocolate milk and most fruit juices are full of sugar. The frequency of sugar intake is more important than the amount. Sweet snacks are more harmful alone than when eaten with a meal.
Refrain from putting your baby to bed with a bottle, or let them walk around the house with their bottle. Sucking on a bottle filled with sugary liquids or milk for long periods of time can rot your baby’s teeth. If your child loves juice then give them juice in a cup, watered down. Try and aim for 1 year of age to be off the bottle.