Open mic performers are expected to arrive early and sign up for a chance to perform. Just because the night is "open" and there are no predetermined sets or performance times doesn't mean performers can just show up and play whenever they want to. Open mic nights usually work on a "first come, first served" basis, meaning that people who really want to perform need to show up as early as possible and sign in to ensure a prime slot. No one should expect a slot if they don't comply with this rule.
Performers at open mics are guests of the venue and organizer of the event. Whether or not performers have a professional level of knowledge of stage equipment and protocol does not mean they can walk into the venue and start tinkering with mixing boards, monitors or patch cords. While performers should be aware of the basics of adjusting a microphone stand and/or plugging in a guitar to an amplifier, performers should adhere to the rules of the event at all times and only touch equipment when given permission by the open mic organizers. When doing so, performers should respect the equipment and treat it with care.
The number of songs allowed and/or set length limit depends on the open mic event rules. Performers should adhere strictly to the parameters of the event to ensure a smooth event that ends by the time the organizers need it to end by, as well as to allow all of the other performers an equal share of time. For example, if a performer is allotted a set of three songs or 15 minutes and has finished two songs with only 1 minute remaining, he or she needs to forfeit playing another song or play a very short song.
Staying for the entire open mic event is expected of all performers. Performers are most likely music fans themselves, so they should have no problem watching other performers out of respect, as well as to take in some pointers. Performers in the audience should be quiet and attentive to the performer currently on stage. They should applaud for each performer, regardless of whether or not they enjoy the music.
An open mic night might be a haven for amateur performers, but even amateurs should be professional in their performance. This includes being totally prepared when on stage. Performers should be in tune before getting on stage and have all of their equipment set up by the beginning of their time slot. Performers should also know exactly what they are going to be performing, having chosen a set list beforehand.