There is no "normal". It depends on what you want to hear and what you don't want to hear. Everyone is different.
For example, you may want to monitor FD but no PD 24/7. You set the FD under the threshold and the PD just above. If you heard FD talking about something police related and you want to monitor all the PD groups, you increase the threshold. If it is just one PD group, you can lower the priority for just that group.
I look at all the groups in the system and assign numbers to the groups based on monitoring all the time, some of the time, and never. Then within those ranges, I look at the all the time group and decide who is a high priority monitoring target and make them the lowest. In the end, I want to be able to control as much as possible
I rarely see private calls so I have left the RIDs alone but the same applies. If you want to hear the private calls, have the threshold above 50 and the option turned on. If you don't turn it off. If you want to hear certain ones, have the ones you want to hear below and the ones to ignore above.
chris