There are already some posted lists of Jam Session Etiquitte on the web. However, here is mine, however redundant or obvious it might seem:
|OMG, what if I forget the changes?|
|These folks look like a BAND!|
3. Have a tune, or several tunes in mind. Unless you are very experienced and know a boatload of tunes and never get stumped, you should think of a tune you know very well and ask the leader of the session if that could be the tune that you play on. Hopefully, this is a tune that you have practiced at home, and you really know it, not sorta know it if there is a chart handy. Furthermore, if a tune is called that you don't know, write down the name of the tune and learn it for the next time. And if you need to look at the fakebook, I don't discourage that. However, the next time you come to the session, you should try to be familiar with the tune.
5. Don't wear out your welcome. Again, be respectful: while you might think that you have thirty-five great choruses within your grasp, you probably only have two.... three, tops. Unless your name is Kenny Garrett, or Herbie Hancock, or Sonny Rollins, you should not over do it. "Say what you got to say, and get out!" is the advice that's usually given. Build it up and leave them wanting more. Again, people will dig you for it.
If anybody has suggestions to add to this list, I'm open. Hopefully, my PSU students will read this before the jam tomorrow(Friday 3-5 in LH 47....)