Preachers are not perfect, not by a long shot. Not even the really, really great preachers who seem to churn out amazing sermons week by week are perfect. Not even the most revered preachers of the past who have produced thousands of outstanding sermons in their lifetimes were perfect.
Consequently, preachers are not always right. Heck, not even all of the Apostles were right all of the time, so you cant really expect yourself to be, nor can you expect it of the person standing in the pulpit on Sunday morning.
Because of this, preaching should always be received with care and discernment, and most importantly with reference to the Bible. If the preacher says something that isnt in the Bible, then you have permission to question it, indeed it makes you noble to do so as it says in Acts 17:11
Now these Jews were more noblethan those in Thessalonica; they received the word with all eagerness, examining the Scriptures daily to see if these things were so.
Be sure though to do this questioning in love. Its no good questioning every word the preacher says just to make yourself feel theologically superior, and it certainly isnt building you up if youre tearing them down. Aligning yourself with the Bible means being discerning, but it also means giving people the benefit of the doubt. Dave Bish wrote in a recent post today I choose to assume the best of others, this is a sentiment we would all do well to adopt.