What I look for is the rejection of modernism, expressed in two main ways: Firstly, a deep, traditional, Catholic understanding has moral absolutes. We talk of good and evil, right and wrong, without relativism. We recognize the role of the subjective but do not use it to replace the objective.
Secondly, we have a concept of authoritative teaching (even if there are disagreements among us about details). The Catholic Church has the authority and ability to teach the truth in a way that no other institution does. Scripture is true and from God. So is Tradition. The Church has the ability to interpret and teach these.
There are also specific issues which are good indicators of a traditional Catholic approach. We believe that Catholicism is uniquely true and valid, not simply one religion among others, nor an interchangeable variation of Christianity.
We understand that the Blessed Virgin Mary is our Mother and our Queen. We have a deep visceral attachment to her.
We understand that error has no rights. There is no right to spread wrong and false ideas.
We understand that there is such a thing as natural law, know what that means, and have it as the basis for our view of sɛҳuąƖity and marriage.
We understand that human life begins at conception and has a right to life. (Some non-Catholics understand this, but it should be obviously true to everyone, so that is not surprising.)
We understand that the religion of the Old Testament was completed by Christ and has been superseded. The Hebrew people were chosen to bring the Saviour to the world and that has been accomplished. Modern Judaism is centuries of accuмulated human traditions, formed by the rejection of Christ and opposition to Christianity. We are skeptical of claims of "anti-semitism" and understand that these are typically to tool for social and political manipulation.
I think that Catholics would normally have all or most of these characteristics since they are all interconnected. Having this cluster of ideas is a better indicator than trying to rely on one specific issue.