It looks like you're new here. If you want to get involved, click one of these buttons!
Having done 5 jams now - starting as someone who hadnt played live for over 20 years (only returned to guitar five years ago after a 15 year 'break'), I thought Id share my tips and tricks from attending these events for anyone else whos starting out. All my own opinion and experience - so may not work for everyone. Feel free to chip in with your experiences!
Before the Event
Its worth selecting two songs to learn - you might find that if you only sign up for one, you really want to do another on the day, so worth being prepared for this.
Create a song sheet - this will help you learn the song and is invaluable if you want someone to help you out on the day (who probably wont know the song very well if at all) - there will be another post on how to do this.
If you feel you need to simplify the part you're playing - do so. I only play one chord strum at each chord change when Im playing and singing (As I cant do both well at the moment) - theres other guitarists who can fill in any other bits, so dont feel pressured into trying stuff you arent happy with on the day. Thats why it helps to have had the run through in the practice rooms. Do your bit well, build your confidence and then learn and progress for the next jam.
Practice playing the songs standing up! I even try playing them with my eyes closed - so I will one day not need to stare at the fretboard, this also stops you relying on the song sheet (as you cant see it!)!
If the song fades out on the CD version - ask the others how they propose to finish it (Live versions on youtube are good for showing examples of this)
You can also learn the songs when away from the guitar by singing the chord names along with the track in the car - its something JustinGuitar does in his tuition videos and it helps your brain retain the chord sequence with the lyrics.
If you need any pedals to boost your sound - get a small simple pedalboard ready for the day (and power supply)