Like many parents, you seem concerned about helping your baby to be healthy and well. The complete overload of parenting advice literature indicates that you are not alone, and that there are many philosophies about how to raise children. The best thing that you can do to help your child be healthy is to be concerned and involved with your child's life and healthcare.
Routine visits to the pediatrician
at the appropriate ages and when concerns arise is a great place to start, but it is only a start. Your example of healthy living will be the real key. Eating a well balanced diet without fast food and with plenty of exercise will teach your child that what you are teaching him or her is important. In fact, the healthy choices of parents is one of the best predictors of the choices that the child will make later in life. Breast feeding (a healthy choice for both you and your child if you are able), lots of time interacting with your child (especially reading and playing), and a good support system will give your child the opportunity to thrive. As your child gets older, remain involved and supportive (and make regular visits to your pediatrician) and you will be giving your child the best.