The ordinary practices observed in any ham radio activity apply to repeaters. Listen first, listen some more, and then jump in. Keep transmissions short, leave gaps for others to join, identify yourself (call and also first name). Keep language clean, and realize there may be many silent listeners. You don’t really know how many people you are talking to!
During a conversation, wait to respond until you hear the courtesy tone after the other party stops transmitting. Most repeaters have timers which will shut down the repeater for a while if a user’s talk time exceeds the time-out period. The courtesy tone indicates that the timer has been reset. Jumping in before the tone means you only have whatever is left on the timer from the previous transmission.
It’s best to wait longer, at least until the end of the “repeater tail”, the period of time the repeater transmits after the other party “un-keys” or stops transmitting. Waiting even longer, especially during commute hours, will allow other hams space to join the conversation or to request use of the repeater for a more urgent call to another ham. This would apply also to repeaters without the courtesy tone.
To start a conversation when a repeater is idle, call someone you expect to be listening, or just throw out your call with something like “W7AND monitoring” or “W7AND listening”. “CQ” is not generally used on FM repeaters. To join an existing conversation, wait for a gap and quickly inject your call, or perhaps the word “comment”. You may have to do that more than once and wait for the parties to conclude a train of thought. Reserve the term “break” for an emergency situation.
Double trouble: A common problem during any radio interchange is the “double” when two parties transmit at the same time. This becomes troublesome when there are several hams sharing the same conversation. It’s not a cardinal sin, but you will only know you were part of a double after you un-key your mike and another ham tells you about it, or you hear another party in the middle of his half of the double.
In many cases the conflicting signals of a double will be unintelligible, but in others the stronger signal may “win” and be heard, with the weaker signal being heard only as a strange buzz. Keeping transmissions short reduces the magnitude of the disruption. It is also helpful to direct control to the next participant in some consistent order, by name or call, when you finish talking.
Hams use various methods for handing the mike to another participant. Some use “over”, or “go ahead”, or just “go”. Others just un-key and let the courtesy tone or the repeater carrier drop indicate they’ve stopped transmitting.
When you are done using the repeater, sign off by saying “W7AND clear”, or “W7AND clear and monitoring”. This lets other hams know the repeater is available after all contact participants have signed off.
Identifying: The rule says every ten minutes and when finishing a contact, but adding one at the beginning is common courtesy. Repeaters themselves identify and become reminders for the users to do so as well.
Signal reports: The usual RS method isn’t used in the FM world. The more useful report is a description of the effective “quieting” with terms like “full quieting”, or “readable with some picket fencing”, or “some hash but readable”, or “lots of dropouts and mostly no copy”, etc.
Distinguish between the strength of the repeater signal and the user’s source signal. If the repeater is coming in at full strength, then a marginal signal is probably the other parties location/power/antenna, etc. But if the repeater signal is weak, it is probably your problem.
If others are having a lot of difficulty hearing you, bail out unless it is an emergency. On FM repeaters, hams get annoyed when they have to work too hard to dig intelligence out of the noise!