Jam Etiquette

You've been looking forward to do some picking for a whole week and today is the day. Usually it's a lot of fun, sometimes not. Here's how you can make sure each time is a great time:

Bottom lines:

Be in tune. Before starting and whenever in doubt, use an electronic tuner.
Be on the right chord.

Remember the chord progression.
If necessary, watch the left hand of someone who knows the chords.

Stay with the beat.

It helps if you:

Recognize common guitar chords by sight even if you don't play guitar.
Help with the singing. Knowing the verses to songs is a key ingredient.
Suggest songs easy enough for everyone to follow. Be aware of common denominators of ability when picking keys and tempos.
Know the basics of simple key transposing, such as when capos are used.
Help others be on the right chord, tuning, etc.
Watch your volume.

Allow featured singer/soloist to be easily heard. If you can't hear him/her, get quieter.
When it's your turn, make sure you're heard.
Be aware that your instrument (banjos especially) may not seem as loud to you as to someone who's in front of it.

Know the traditional unspoken ground rules (see below).
Give everyone a chance to shine. Be encouraging.

Traditional unspoken ground rules:

Whoever is singing lead or kicks off an instrumental usually leads the group through the song, signaling who takes instrumental solos ("breaks") and when to end.
Typical arrangement formats:

On a song when there are few or no instrumental soloists: The singer starts tune any way comfortable, others join in, play until verses run out. Or the singer can give a solo to anyone willing, following format:
On a song when some instruments can solo:

Break ("kickoff"), verse, chorus,
Break, verse, chorus,
Break, verse, chorus [optional: add solo(s) and final chorus]
On instrumentals, the same person usually starts and ends, with solos going around in a circle to those willing. Most common end: double "shave and a haircut" lick.

Regarding solos ("breaks"):

Breaks for songs generally follow the melody and chords of a verse.
At the beginning of a song and following each chorus, the singer offers breaks. Head signals and body language are used to offer, accept/decline.
If no one can solo, the singer just keeps singing verses and choruses to the end.
If there are more soloists than there are verses of the song, some solos can be grouped together to give everyone a turn. Or the singer can repeat verses to lengthen the song.
If there are more than enough spots for breaks, some soloists can take an extra turn.

If an instrumental soloist starts late, listen for whether the break is starting from the top or from a later point in the song. If different players realize they seem to be at different points in the song, try to resolve it quickly, usually by falling in with the soloist, even if he/she is mistaken.
When the lead singer doesn't start a verse on time, keep playing the root chord and wait until the singer starts before going to the chord changes.
Sing harmonies on choruses only, normally. Verses are sung solo. But in less advanced jams, people may often sing along on the verses too, even if not singing a harmony.
Use signals to help everyone end together: Foot out, hold up instrument, end after "one last chorus" or repeat of last line. Listen for instrumental licks that signal ending.

Etiquette stuff:

Some key participants may have main influence over the choice of songs and who gets to do what. Be respectful of the situation. Fit in as invited.
Instrumentalists, be mindful of when others want to solo or do featured backup. Give them space and take turns being featured. Don't compete!
Re-tuning: wait your turn. If someone is tuning, avoid any playing, or perhaps (if you're sure your instrument is in tune) offer notes matching the open strings of the other person's instrument.
In more advanced jams, often the "classic" arrangement of a particular number is followed, including choice of key, which instrument solos when, harmony parts, etc. However, if the classic version is in a key that doesn't work well for the lead singer, the singer calls the key and the others adapt.
If you don't fit into one jam, look for another or start another, or just stay and listen. (Note if there are already enough of your instrument in the group, or if the speed or difficulty of the material is out of your league.) In some situations it's OK to play quietly in an "outer circle", not trying to be heard in the inner circle.
Pay attention and learn from experience.
The circle - stagger the players so there's balance and variety: Don't have two of the same instruments standing or sitting next to each other.
Keep your eye out - make room for new players so they can enter the circle at any time and feel welcome to do so.
Every one in the circle plays the same tune or song at the same time.
Announce the songs key and title loudly before starting each tune or song. Repeat as necessary.
Announce the chords if some one is not familiar with the tune.
Breaks go around clock-wise. Each player, regardless of musical ability, gets a turn.
The tune, or song, is not finished until each musician in the circle gets a break.
Players may skip their turn at a break at their discretion - not at the discretion of others. Signal your pass by taking a step back or shake your head.
If a player falters during a break: he/she is allowed the opportunity to recover before the next player in the circle takes over. Other players keep the song going while the breaker tries to recover - a "miss" is never a strikeout. Once recovered, the break reverts back to the original player.
Players should clearly signal the next player in the circle if they want him/her to take over.
Other players lower their volume while some one takes a break.
When a break is to be played, statements like “banjos” or “guitars” or “mandolins” or “fiddles” should be avoided. Each individual should be allowed to play a break without competing with similar instruments during that break.
When the player next to you does not know the chords and you do, tell them quietly.
Groups that have split off from the circle should sit/stand far away enough and lower the volume of their playing so they don't interfere with the circle.
Anyone playing along who is not in the circle does so at a lower volume and does not "compete" with the circle.
Jams are not the time for music lessons. Don't ask other players how to play a certain lick during a jam. Save it for a one-on-one later, or a workshop.
Every one, regardless of musical ability, should be invited and encouraged to join the circle.
Make sure not all songs are hundred mile an hour instrumentals, allow for a change of pace and pick a few slower ones to give every one a breather.
Tune your instruments! If your instrument is out of tune it'll drive other players bonkers and easily distracts them into playing mistakes. If you don't know how to tune, ask someone to help you or buy an electronic tuner. They are easy to use gadgets you can pick up for as little as about twenty dollars and up and properly tuned instruments simply sound better.

Food for thought: "a person with whom one shares close ties of liking," or: "a person who is often in the company of another," or: "a person whom one knows casually" -- guess what, they are the dictionary definitions of the word friend. Treat your fellow circle jammers accordingly and enjoy.