The main boundary is Holy Communion. Receiving the Eucharist belongs to baptized Orthodox Christians who are prepared, fasting, reconciled through confession, and under pastoral care. Attending the Liturgy and receiving Communion are therefore not the same act.
How to participate reverently
Stand with the faithful when you can, sit when needed, listen to the hymns, and follow the Gospel, Creed, litanies, and Eucharistic prayer with attention. You may light a candle if that is customary in the parish. You do not need to copy every gesture immediately.
He said to them, “Come and see.”
The best first posture is humility. The service is not built as a classroom lecture; it is the Church worshiping God. Understanding grows as you return, ask clear questions, and connect what you saw to Scripture, the Liturgy, and Orthodox teaching.
What to ask first
Ask about the Liturgy before asking for a decision point. Good questions include: “What is happening at the altar?” “Why does the Church pray this way?” and “How does someone begin learning the faith here?”
If your question touches Communion, confession, baptism, marriage, or conversion, speak with the priest. Those are pastoral matters, not only informational topics.