I have vey basic criteria for whether or not I believe someone is frum. Does he/she keep Shabbos properly, keep a strictly and unquestionably kosher home (though it might not be the specific hechsher that I hold by), does the man daven every day (even if it is b’yechidus, though minyan is the proper thing to do), and does the woman keep Taharas Hamishpacha? Of course, one hopes they dress and act tznuim, send the kids to Yeshivah, and follow the Torah, but if they are doing these things they are still fulfilling Ratzon Hashem.
If you want to nitpick, you may, but I said, “frum” not Yeshivish, Litvish, Chassidish or any other “ish” except to be mishtadel l’hiyos one.