There are several principles that must be considered, when establishing sound doctrine. 
1. We know and acknowledge that the Word is inspired by the Holy Spirit. 

2. The Word is profitable for doctrine, reproof, correction, instruction in righteousness 

3. The Word does not contradict itself 

4. any doctrine of men that conflicts with even one relevant passage in the Holy Bible, must be revised to satisfy that relevant passage; or else, it must be discarded, for it is a half-truth doctrine 

5. the WORD is truth 

6. the scriptures must be taken as a whole 
7. the context in which a passage is found must be considered in interpreting scripture.

I am not saying that these are all the principles, but they are certainly important,