Hey Guys. I'm Andrew and I'm a Non-Denominational Protestant looking into Orthodoxy.
We're on much the same path, it seems. I was Evangelical before, but my connection with any particular denomination was tenuous at best, so you could call me pretty "non-denominational" too.
As to "the main defining points" as distinct from non-denom Protestantism...wow. Big question. But we could start with:
1. Church Authority
2. Church Hierarchy
3. Tradition as the Rule of Faith
4. Veneration of Saints and Icons
5. Perpetual Virginity of the Theotokos
6. The Word "Theotokos" (Mother of God) itself
7. The Single Procession of the Holy Spirit
10. Apostolic Succession
11. Funny Hats
12. Non-Judicial View of Salvation
13. Holistic View of Man (Body and soul, not a soul trapped in a body)
That should be enough to provoke some discussion, at least.