The bible must be our supreme authority in all matters of faith and practice. No questions asked.
That said, I have found it helpful to look through different Christian documents (creeds, confessions, statements of faith, etc.) in order to help me clarify what I believe and why.
Based on their content and/or their historical significance, the following are my 5 favorite non-inspired Christian documents:
The Nicene Creed (A.D. 325)
The 95 Theses (1517)
The Canons of the Synod of Dort (1618-1619)
The 2nd London Baptist Confession (1689)
The Abstract of Principles (1858)
What are your favorite Christian documents? Why?