What is the best way for the individual to maintain the proper balance
of potassium/sodium to prevent disease?  Please cite the best
books/articles on the subject.

There isn't just one single answer to this. It depends upon the
individual. For instance, my own sodium and potassium intake must be
kept high because my colon has been removed, and I can become
dehydrated very easily. My friend, who has hypertension, must keep her
sodium intake very low. Maintaining "the proper balance" is a very
different matter for the two of us.