YES!
I used to host open jams, and still participate in them. They can be really fun if the house band is good.
Here's the Top 10 open mic rules I go by:
1. Don't go first, but if you're new to it, try to play early in the night. Ask the host if there's a list, and that you're interested in playing a few. When you get up on stage, announce "it's your first jam," the crowd will be warm and receptive. LOL It's blues jam virginity they get to witness a right of passage. 
2. If the house band sits in on your little set, choose tunes or at least keys that everyone knows. You may be expected to sing if you pick the songs. The house band will expect you to pick the songs when you sit in.
3. If you're singing and picking the songs, you're the band leader. Everyone will look to you for changes, stops, and who's turn it is to solo. Communicate visually with body language. They will follow... take mental notes how others do it before you go on. If someone is having a hard time following your song, make sure they can see your guitar neck so they can see the notes/chords you're playing.
4. Don't take all the solos. Take a couple measures, then "nod" to the other guitar player when it's his turn to solo. Give the keyboard player 'some, and even the bass player if he sounds like he'd take one. Everyone appreciates what I like to call "traffic control." This is a major part of navigating through an open jam.
5. If you want to go back and forth with the other guitar player (lick for lick) in the middle or at the end of the song (cutting heads) talk to the other guitar player about it before hand so you can plan a little how it's going to go so it's entertaining for the crowd and so the band doesn't continue to play through it.
6. Be humble and happy to be there. If the place is "clicky" you'll have to show them you're cool enough to hang and not bad enough to scare everyone out of the bar. Sometimes they allow their friends to go first even though you arrived before them. Let it slide... if you like it - one day you might be one of those friends who just seems to have a spot reserved. lol
7. don't go into jazz odyssey. Most people in attendance will be other musicians and perhaps their friends. They won't be judging you, or scrutinizing your playing. Open mics are fun only, not a contest.
8. Be able to "stay in the pocket" meaning don't solo every change you get, and don't overpower the keyboards or the other guitar players. Make sure the sound is balanced and that it's not "all about you."
9. it's usually a cool idea to walk around after you're done and ask how it sounded. It's a great one-liner to spark conversations if you don't know anyone. And you could get a few pointers. If you show up, play, then leave, it might not be a good first impression. Open mics are great for musician networking, and most people put on their best face to build relationships.
10. Bring an amp, and the least amount of pedals possible. they want to get you on and off as quick as possible. Lots of times, the list gets full and everyone doesn't get to play. In fact, leave your amp and pedals in the car and just bring in your guitar. Make sure the amp is out of plain sight. The house band might want you to plug into their rig. Don't mess up their EQ, you might want to ask the person who owns the amp either if it's ok to adjust his settings, or if he wants to tweak them while you're playing. If it sounds like cats having sex, then at least you'll have a good excuse 
I realize these could have been listed in a better order. apologies!
have fun!
Nic
- Nic from Detroit...
posting on JB's Forum since 6-2-2006Ask me about my handwound
Great Lakes Guitar Pickups Since 2010, Bonamassa fans have taken advantage of my JB friend discount = my cost + shipping.
