D is for Doctrine

Doctrine (noun): a codification of beliefs or a body of teachings or instructions, taught principles or positions, as the essence of teachings in a given branch of knowledge or in a belief system. 

The word comes from the Latin word doctrina, which simply means "teaching." It can be seen as a framework for understanding particular beliefs.

In The Salvation Army (my church), there is a Handbook of Doctrine which can be downloaded and studied. The Handbook details the 11 Articles of Faith which since 1878 have been the basis of The Salvation Army’s witness to the Christian gospel. Such a document equips anyone to distinguish between truth and incorrect teachings.

There's nothing worse that following something blindly. Always question, always struggle to understand, always seek to apply this to your own life. 

2 Timothy 3:16-17 (NIV)

16 All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness, 17 so that the servant of God may be thoroughly equipped for every good work.

Teach

Deuteronomy 6:4-9 (NIV UK)

Hear, O Israel: the Lord our God, the Lord is one.  Love the Lord your God with all your heart and with all your soul and with all your strength. These commandments that I give you today are to be on your hearts. Impress them on your children. Talk about them when you sit at home and when you walk along the road, when you lie down and when you get up. Tie them as symbols on your hands and bind them on your foreheads. Write them on the door-frames of your houses and on your gates.