I like John Shore's Huffington Post piece, "Ten Ways Christians Tend to Fail at Being Christian."
Here are my favorites:
1. Too much money.

3.  Too quick to believe that we know what God really means by what he says in the Bible. The Bible is an extremely complex, multi-leveled work. We're sometimes too quick to assume that we grasp its every meaning. Take this passage, for instance, from Luke 8: 9-10: "His disciples asked him [Jesus] what this parable [of the sower] meant. He said, 'The knowledge of the secrets of the kingdom of God has been given to you, but to others I speak in parables, so that, "though seeing, they may not see; though hearing, they may not understand."'" Huh? And that's Jesus "explaining" what is generally regarded as one of his most readily understood parables! Are we really all that confident that we always know exactly what Jesus meant by everything he said? Wouldn't we do well to sometimes admit that the words attributed to God manifested on earth are just a tad, well, Greek to us?

10) Too uneducated about Christianity. Generally speaking (which of course is the most offensive way to speak about any group of people), Christians tend to embarrass themselves by knowing so little about either the Bible or the history of Christianity. Believing that the Bible is the word of God, for instance, is one thing; knowing nothing about the long process by which men decided which texts would and wouldn't make it into the Bible is another. It's not that all Christians should be full-on theologians or historians. But if you're a Christian who doesn't know the Great Schism from The Great Santini, or the Diet of Worms from ... well, the diet of worms, then you've got some homework to do.

I'd probably re-work that last point and encourage us all to learn the whole Bible rather than learning parts of Church History. And I'd encourage us to spend time praying and in silence so as to listen to God.

Got any other great ideas?