A lot of times when I work concerts and similar events, other people are hired to run the sound. If you don’t yet know what the plan is for sound, that’s a good thing to ask about. Have a conversation with the sound people on the day of the event on how you can work together. Sometimes they appreciate an extra set of hands. Other times, they only want people with their company touching the equipment. It’s good to talk through the transitions together as much as possible so you don’t get in each others’ way. Do you have info on what instruments each performer is bringing and what kind of mics they need, and info on seating and music stands? Sometimes producers have gotten sketches of performers’ stage set ups ahead of time, and if you can make copies for sound and yourself that’s really helpful.
In these situations, it may be that you as SM just need to get the performers to the stage on time, and aren’t responsible for the sound at all. If there are lots of different performers, you may want to assign your ASMs so one is always with the group that is “on deck” and another waiting to escort the current group away from the stage, where you’ll want to avoid over crowding, with the third ASM staying with the group that is 2nd in line. Find out what kind of turn around time the producers want between groups. Sometimes they say “as soon as possible” and then are disappointed when it takes 15 minutes to reset the stage, so if possible, encourage them to build into the schedule a couple minutes to strike and reset.
Bring snacks and water for yourself in case things get hectic, also extra paper and pencils, etc, so you can make cheat sheets for yourself and others. Every concert is unique, so just keep your eyes open and be ready to go with the flow. Also, there is a lot less mystique in a concert setting, so if a chair or mic or whatever is out of place, don’t be shy about walking on stage and fixing it, audiences are used to seeing that.