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.