Start by playing with one or two others to build your ability and confidence.
Simulate playing with others by practicing with instructional CDs that have rhythm tracks to play along with. You can also test your skill at playing along with the CDs in your music collection.
Learn to recognize the commonly used guitar chords so that you can follow chord changes with a guitar player by sight.
Test your skills at picking up the chords to songs by ear by trying to learn a song from a CD. Unfortunately, I do not have the space to get into that subject further, but that is an excellent way to learn. The more knowledge and ability you have to work with, the easier this will be, and there is a lot of information throughout The Banjo Encyclopedia on which to build your foundation.
Use a song list as a map and measuring stick to see which songs you can play well enough and which ones need more work. Check off the songs when you are satisfied. Using a song list instead of tablature is another excellent way to decrease your dependency on tablature.
Use the many chapters in The Banjo Encyclopedia to build your knowledge and ability base to better prepare yourself for getting out there.
Learn techniques and skills that will fit into many songs.
Learning beginnings, turnarounds, and endings will help get you started and stopped. Improving the “package” in the middle can be done over time.
Practice and preparation will build confidence.
Be sensitive to others, both musically and personally. This will make the experience more enjoyable for everyone.
When tuning, be considerate by not tuning while someone else is or when it detracts from the music being played. By all means, however, be in tune as best you can at all times. Playing out tune can be a jam breaker!
Study Chapter 14: Playing in Different Keys, Tunings, and Using the Capo.