All coordinated movement of worship leaders are processions. Processions happen to the church and to the world and to parts of the church. A general rule is that processions happen in order from individuals with the least specific duties in the worship to those with the most specific duties in the worship. Below is a general outline for an opening and closing procession. Individuals in [brackets] are less normative.
[Visiting, Vested, but non-assisting Laity (ordinands)]
[Visiting, Vested, but non-assisting Deacons]
[Visiting, Vested, but non-assisting Priest]
[Lay Eucharistic Minister(s)]
[Gospel Bearer (subdeacon)]
[Subdeacon (alt.)] Celebrant [Deacon (alt.)]
[Visiting, Vested, but non-assisting Bishop(s)]
Generally any procession in the church follows that pattern with whatever people necessary for the function that is occurring at the arrival of that group. The above allows for a full pomp and circumstance ceremony. Vergers are basically brought in when traffic control is necessary but should be as invisible as possible.
The three main exceptions are Gospel processions, Baptismal Processions, and Funeral Processions.
Gospel processions from the altar flow out normally: [Verger] [Thurifer] [Crucifer] [Torches] [Gospel Bearer] Deacon/Priest. BUT return with the Gospel Book at the front of the procession, generally in reverse order.
In Baptismal Processions baptismal candidates, families, and sponsors follow the rest of the procession.
When a procession is occurring with the remains at the end of the funeral from the church to the graveside/hearse or from the hearse to the graveside the following order is followed: Presiding Minister, Remains, [Crucifer], [Torches], immediate relations, [Assisting Ministers], [Choir], Mourners.
Marriage processions are a matter for another day.