Often, Satan's strategy is to poison us slowly, over a long time. The end result is all that matters to him. With many of us, he knows he can't take us out in battle -  he will lose a direct confrontation, so he sneaks us a bit of poison to swallow  - a small lie here, a tiny lie there. He tries to get us to compromise in small ways not big. He isn't blatant. He mixes a bit of truth in with his lies to make them more palatable,  easier to digest. You sip a little poison every day and you don't notice till it kills you.

 Small doses weaken the immune system (the ability to recognize truth) till the day comes when he presents you with a large lie - a major false doctrine, that's offensive to the Holy Spirit-  and you swallow it whole without question -  especially if it comes from someone you trust, like a popular Christian speaker or author or your pastor. If your pastor says it, it must be true, right? Let the Holy Spirit examine everything you digest, let Him pick out the bits that are not from Him -  let Him teach you how to shine His light on all you are taught. Learn how to recognize His voice, His touch, His gentle nudge deep inside you, telling you when someone is not authorized or anointed to speak on His behalf -  whether prophecying,  preaching or teaching. 

Be willing to expose and reject teaching when you sense it is not of the Holy Spirit.  If it's not His voice coming from another, do not accept it. Even the very elect may be deceived. Anyone who gets offended when you question their teaching probably shouldn't be teaching.  Love truth more than the one sharing it. Don't put them on a throne above you -  where they cannot be disputed or held accountable for what they teach. If your sitting under a minister like that - get out. Don't swallow the poison! No matter how good it tastes and no matter how many other people are swallowing it. 

I've been to churches where the pastor has several cheerleaders scattered throughout the congregation, yes men, if you will, who shout "AMEN PASTOR! PREACH IT! throughout the sermon. I've heard these pastor's teach  blstant, quite obvious (to me), false doctrines while the yes men shout Amen! Yes pastor! This does the pastor (and the congregation) no good at all. It can stroke his ego and make him think he's teaching truth when he isn't.  It puts him in a place where the praise of men can replace and become more important than the praise and honor God gives, and it makes the baby Christians, and any non-believers present,  think they are hearing truth -  which becomes much more difficult to hear over the sound of Satan's laughter. 

"None calls for justice, nor any pleadeth for truth: they trust in vanity, and speak lies; they hatch serpent's eggs, and weave the spider's web: he that eats of their eggs dies, and that which is crushed breaks out into a viper."