They aren't many.... but they are big ones.
1.) Ignorance of Religious History- I don't expect everyone to be a scholar of Religious History, but there are some facts everyone should know.
I've heard WAY too many Southern Baptists (I live in Virginia) claim that Catholics aren't Christians. I've stopped trying to correct them, it confuses them and annoys me. I think that every Christian should know that up until 1054 there was *1* denomination. That's it! Between 1054 (The Great Schism where Roman Catholicism and Eastern Orthodoxy split) and 1517 (Luther's 95 Theses) there were *2* Denominations. After that it gets a little more complex. But the common thing is that ALL of these churches believe in Jesus being the son of God and all.
I tried to teach Medieval History to rural Baptist Virginians. It was difficult. Medieval society is built around the Catholic Church... which I had to explain... over and over.. was christian.
I won't even go into the fights I had when I did the state mandated World Religions unit.
2.) Cherry Picking the bible for verses. First, go read this. I'll wait.
We've all heard the "God is against Gays" argument. We've even seen the verses that people say support that. No one ever talks about the context of those verses. Talk about Leviticus and Jewish Law and some people look at you funny, because they never learned that the Old Testament is from the times BEFORE CHRIST! Since most arguments that are supported by Biblical verses can be disproven by other Biblical verses (My brother loves doing this), let's look at the bible.
The bible is a few things. 1.) It's an anthology. People actually sat together and decided what to include and what to exclude. 2.) It's a translation of a translation of a translation. A religious game a telephone. It is known that the the King James Version of the bible was translated in such a way that it would better fit the Church of England. Yes, instead of structuring religion around a bible, structure the bible around the religion.
3.) Blind Faith.
Religion isn't something you should blindly follow. It's something to be studied. Why do they believe this? When did that practice start? What is the context and history around these practices? Without answering those questions you can't fully participate in any religion. God never wanted you to turn off your brain and do what the guy in the pulpit says. According to many religions (and Joan of Arcadia) you were given Free Will! Use it! Study not only the bible, but the history and traditions that surround it. Yes, I believe that every Christian should know the basics of Judaism. Why? Jesus was JEWISH! How do I know? I read it in the BIBLE!
I have no problem with organized religion. I do have a problem with people that simply refuse to think for themselves. Think, learn and study. Use that Free Will that God gave you.
You'll be glad you did.