How do we know when something is Sacred Tradition?

I had an RCIA catechumen ask me a question about Sacred Tradition (I guess it’s really two questions). It’s a simple enough question, but I’m stumped in providing a satisfying answer. His question is, “How do you know when something is Sacred Tradtion; are they written down somewhere (outside of Scripture, obviously?)” Or is Sacred Tradition determined through historical/doctrinal discovery?

The following links should help answer your questions about Church Tradition. If you have any further questions, please contact Catholic Answers directly.

Recommended Reading:

Scripture and Tradition
What’s Your Authority?
The Problems with Primitivism
