I didn’t know much about Catholicism growing up (sadly, there was significant antipathy, but that’s a subject for another thread another time). However, I bought myself a copy of the Catechism and got a profound respect for the Church, even if some of the teachings were different than what I was accustomed to.
I now find myself hoping to attend a Catholic University (in order to study Nursing because I think it ludicrous to ignore the spiritual aspect of healing; again, best for another thread).
Folks, I’ve never been around you. I’m afraid of saying The Wrong Thing. Y’know, I saw three Sisters during my campus tour today, and I didn’t even know the proper form of address.
What’s the solution? Keep the conversation light, and don’t bring up religion?
Feel free to take this thread as seriously or as lightly as you like…
Most catholic universities these days aren’t even much more than slightly majority catholic. As long as you’re respectful (even in disagreement) you should never run into any problems. Just understand that some of the code of the school is going to be based on catholic moral teaching, and that those are going to be rules that don’t change (for example, my Catholic University prohibited distribution of recreational prophylactics at the student health clinic)
As to proper forms of address:
Office - Address
Nuns - Sister
Monks - Brother
Priest - Father (Monsignor if the priest has earned the title)
Bishop - Your Excellence
Archbishop - Your Grace
Cardinal - Your Eminence
Pope - Your Holiness
This is all very traditional of the medieval form though, such as:
Nobles - My Lord
Prince/Princess - Your Highness
King/Queen - Your Majesty
Today addressing a bishop as “[arch]Bishop” or “[arch]Bishop LastName” is generally acceptable

chances are you won’t be receiving any cardinals or the pope, so I wouldn’t even worry about those
Oh, and one other thing: if you take the time to visit mass while you’re there, respectful following of those around you in posture (kneeling, standing, sitting, etc) is encouraged with one exception: non-catholics may not participate in going forward to receive communion. We ask this for your own protection as well as out of respect for our sacrament. Since we believe in the real presence, to take the sacrament without proper disposition both morally (which you may have), spiritually (which is attained through the rite of entrance, most generally the RCIA program) and mentally (through education and acceptance of the meaning of the sacrament and the real presence). We believe that if you do not have these three properly disposed that you commit a sin of sacrilage and thereby hurt yourself while doing damage to one of our sacraments. It’s NOT meant as an insult, but rather done out of concern for you and our love of Christ.