That's a good question, how to evaluate it is going to be very POV dependent.
For me it usually boils down to the fruit of the tree thing with the lives of the congregation being the fruit of the teaching of the Church in question.
How do the lives of the Congregation differ from the lives of the seculars around them?
Do they have strong families and purity in marriage or do they mirror the secular world in things like divorce and remarriage, adultery and fornication with sexual relations starting in teenage years and having no relation to marriage, do they send their children to private Christian schools to be raised up in the way they should go or to public schools where they are taught every abomination listed in the Bible and encouraged, even sometimes required, to practice them, etc.. etc., etc.
For the most part, this is how I see things and how I evaluate a church and its teachings above everything else.
But that's my part of the elephant, others will be touching other parts and think differently.
May the Lord bless and guide all of us this day.