St. Vincent of Lerins was an early patrologist. In fact, he laid the ground rules for the study of the Fathers. And he himself was a Church Father, so he had a leg up on the rest of us. The ever-timely Fr. John Zuhlsdorf gives us this on his blog of many wonders:

Today is the feast of St. Vincent of Lérins (5th c.).
He is the fellow who gave us a famous rule for distinguishing true Catholic teaching from heresy. In a work called the Commonitorium, written ostensibly to help us remember the ideas, he underscored the importance of Holy Scripture as a rule of faith. The first thing we do is submit our questions or doubts to Scripture. However, since people disagree about what Scripture means, we must take into consideration the interpretation of Scripture which has been held since antiquity, by the whole Church (universality) and most agreed upon by those who have the authority to interpret.
You might have heard this put in Latin as Magnopere curandum est ut id teneatur quod ubique, quod semper, quod ab omnibus creditum est.

Or you might not have. But you should read St. Vincent and ask his intercession today.