Going to perform at your first open mic?
Playing your first open mic can be nerve wrecking. Often times that nervousness impacts our performance. The key to a great performance is to get comfortable with the environment and people there. Folks are generally there to support one another and have a good time. Even if you mess up, smile and keep going, it's ok.
That said, there are some things you can do to prepare for a great, fun performance. First, make sure your equipment is working properly and you are comfortable getting setup quickly. Often times you will only have a couple of minutes to setup and prepare. Try and get an understanding of the setup/config at the place you will be performing. Clarify, do they have amps for guitars, backing tracks/loops, whatever, or will you need to plug into the PA?
Practice setting up your configurations accordingly.
Before you go:
Practice your song until you can play it in your sleep. Choose something you're genuinely comfortable with rather than trying to impress with difficulty. Most audiences appreciate a well-executed simple song over a sloppy complex one.
Song selection:
Pick 2-3 songs you know inside and out, but plan to only play one unless they ask for more. Choose something that doesn't require perfect timing or intricate fingerpicking - open mics can be nerve-wracking and fine motor skills suffer when you're anxious.
Gear preparation:
Bring your own pick (have a backup), check that your guitar is in tune before you go up, and if you're using electric, know how to quickly adjust basic amp settings. Many venues provide amps, but they're often set randomly by the previous performer.
Mental preparation:
Accept that you'll probably make small mistakes - everyone does, even pros. The key is to keep playing through them rather than stopping. Most audiences won't even notice minor slip-ups if you don't draw attention to them.
Performance tips:
Make eye contact with friendly faces in the crowd, not the intimidating ones. Take a moment to settle yourself before starting - there's no rush. If you mess up badly, smile and restart if needed - people appreciate authenticity over perfection.
Practical stuff:
Arrive early to get familiar with the space and sign-up process. Bring water since your mouth will get dry. Most importantly, remember that open mic crowds are typically very supportive - they're there because they love live music, not to judge harshly.
The first time is always the hardest, but you'll likely find it's much less scary than you imagined once you're up there.