How do you keep an eye out for heretical teachings?

So many centuries after Jesus and his apostles died there are more people giving preference to present day teachers, theologians and philosophers, instead of giving ear to the biblical writers or scriveners than in Jesus' time.

A Book to trust #29 God His Book, God-breathed profitable for doctrine, for reproof and for correction

In this godless world we all should remember that man shall not live by bread alone, but by every word going forth through the mouth of God Which He has provided for the whole world in many Bible translations. Nobody may forget that in whatever language the Bible is inspired by God and as such protected by God's Power so that it can be useful for every person on earth for teaching, for reproof, for correction, and for training in righteousness, in such a way that the person dedicated to God may be capable and equipped for every good work.

A Book to trust #26 Roadmap for life out of darkness

The Bible can be seen as a road map, a form of map that details roads to go to the entrance gates of the Kingdom of God and to to resolve the God-Man conflict and the conflicts between the human beings. That book of books brings us the Voice of God and the voice of the chosen men who like their Creator brings a call to come out the darkness. all those stories should give us an eagerness to learn and to teach others like in did in the ancient days.