Because there is some danger if your child gets too much fluoride, your choice of toothpaste is important. Keep in mind that most brands of kids' toothpaste are fluoridated. They just have different flavors and popular characters on them to make them more fun for children, but that doesn't make it safe for your children to swallow too much of the toothpaste.
If using a fluoride toothpaste, use a small, pea-size amount of toothpaste, so that there is little danger of your child getting too much fluoride if he swallows it. And begin to encourage your child to spit out the toothpaste at a young age.
The other alternative for younger children is to use a non-fluoridated toothpaste, such as Baby Orajel Tooth and Gum Cleanser, until they are spitting the toothpaste out.
Another important topic is figuring out if your child is getting enough fluoride. Children begin to need supplemental fluoride by the age of six months. If he is drinking tap water (either alone, or mixed with formula or 100% fruit juice), and you live in an area with the water is fluoridated, then he should be getting an adequate amount of fluoride. If he doesn't drink water, or is drinking well water, unfluoridated bottled water (most brands of bottled water don't have fluoride in them unless the label specifically states that they do), or filtered water, then he may not be getting enough fluoride to keep his teeth healthy. Talk with your Pediatrician or dentist about fluoride supplements.
Water filters are a special concern, because some of them do filter out fluoride. Counter top filters and the pitcher type filters usually don't remove fluoride, but more sophisticated, point of use filters can. If in doubt, check with the manufacturer to see if the filter removes fluoride.
You should also talk with your dentist about using sealants in your school age child. A sealant is a plastic material that is applied to the teeth, hardens, and provides a barrier against plaque and other harmful substances. Sealants can be applied to the 1st and 2nd permanent molars to help protect the grooves and pits of these teeth that can be hard to clean and are prone to developing cavities, and appropriate premolars as soon as possible after they erupt (usually after 6 years of age).
What about flossing? Flossing is an important part of good dental hygiene. You can usually begin flossing once your child is about 3-4 years old, but they likely won't be able to floss on their own until they are 8-10 years old.