Nearly every client with whom we’ve worked over the years has wrestled with how to manage duplicate contacts in their Civi. Although it’s impossible to eliminate duplicates completely, we do have some tried-and-true suggestions for minimizing them with as little risk as possible.
Creating effective duplicate rules is often more art than science. You want to hit the sweet spot between removing the possibility that contacts are overwritten incorrectly, and setting the rule so restrictively that contacts are more frequently duplicated than not.