"Beware of false prophets, which come to you in sheep's clothing, but inwardly they are ravening wolves." -Matthew 7:15, KJV

There are many false prophets who want to steer God's people away from the truth of His Word. Anytime any preacher gets up to preach, you should have your Bible open to the passage he is using and be taking notes. Some misinformation is intentional, some is accidental (preachers are human after all), but you need to guard yourself against it. This doesn't mean to backbite your Pastor. He should always be supported and encouraged by you. It just means that you need to believe the Bible over what any man says. The sermon is not a time for you to veg-out and be spoon-fed, but rather to be active and grabbing all the information you can to grow, but also be critically thinking with a Biblical perspective. (This is why you should always have your Bible in church.)

"These were more noble than those in Thessalonica, in that they received the word with all readiness of mind, and searched the scriptures daily, whether those things were so." -Acts 17:11, KJV