How do you know if things that irk you are peeves or red flags?

An easy test for distinguishing a pet peeve from a red flag is to look at intent. An involuntary action like snoring or a personality quirk can be a pet peeve. A red flag is a consistent pattern of intentional behavior that is toxic to some extent. 

Something that could have started as an annoyance becomes a red flag when the partner refuses to make compromise even after you’ve communicated about it. The worst people and partners are the ones that not only know their worst qualities, but refuse to change and go so far as to find an identity in those qualities.  

If something irks you about them now, chances are that they’ll only get more annoying. If you’re in doubt, ask your close friends and family for another viewpoint—sometimes love blinds you to what’s in front of you. 

In order to be dating healthily you have to be mature and respectful of yourself and others. A simple pet peeve would not make a significant impact on one’s morals, dreams and goals, and a good partner would not ask you to make such compromises.  

If, as the relationship progresses, you notice that some of those old pet peeves start looking like red flags, you should start assessing if you are giving up too much of yourself for that relationship. A relationship is a give and take, so if you’re all give and no take then you should see the red flags for what they are and back out before you get hurt.