In the church, there is a method by which you recognize visiting clergy.
If you are in the midst of having a service and it is brought to your attention that another Person of the Cloth is present someone (typically an usher or deacon) will approach that person and invite them to sit in the pulpit or at least on the front row.
This is how to honor them and acknowledge them as a colleague or peer.
If you know the person… you may invite them to have a few words. They, in turn, will (during their few words) give honor verbally to the Host Pastor and Clergy, encourage the members in their loyalty to this house of faith and speak words that edify.
This model has been used for MANY MANY years… simply because it works….