Several times I have gone to a recitation of the Rosary or Divine Mercy Chaplet. I notice that many times one person starts a prayer and then everyone else finishes. It didn’t occur to me Saturday when we were doing the Divine Mercy Chaplet for our nation. I realized I was saying aloud what the leader was supposed to be doing. Is the somewhere I can refer to as protocol for times like this. I am used to saying it all myself so it was a bit awkward.
I think it is one of those things that you learn by observation and doing. Even in the Mass, there are prayers we say together, like the Our Father, and prayers we pray responsively, the leader, priest or deacon says one thing and we say another, like the responsorial Psalm.
When you notice there is a pattern, you just go with the flow so to speak. And it may vary from parish to parish or diocese to diocese or region to region. There Is a prescribed order to the Mass but I doubt there is something that covers every conceivable situation in other areas. Plus even the tunes used in Mass and the prayers of confession vary. The priest has options in the Mass.
It is kind of like singing as a group with a leader or director. We are no longer lone rangers or soloists. We are doing it corporately as a body.
Don’t worry about making mistakes. Just amend your practices as you notice they are not in order. I can almost guarantee that most people won’t notice and if they do and they are honest, they will remember when they have done the same thing.