The Ten Jammandments
As a public service, below are the "unofficial" rules of a bluegrass jam.  
By Larry Carlin

I.      Thou Shalt Tune Thy Instrument.
       ~ Electronic tuners make this easy.

II.      Thou Shalt Keep Steady Rhythm.
       ~ Count beats if necessary.

III.      Thou Shalt Take Turns Choosing Songs.
       ~Announce the key. Vocalists always choose their key.
       ~ Choose a song you can complete.

IV.      Thou Shalt Not Speed.     
       ~ Start songs at a reasonable tempo. Speed up according to abilities.

V.      Thou Shalt Signal Who Has The Solo.
       ~ Follow a pattern when taking solo leads.

VI.      Thou Shalt Listen To Others.
        If you can't hear the lead, consider yourself too loud.

VII.     Thou Shalt Welcome Others.
       ~ Include everyone in your jam. Help everyone sound as good as they can.

VIII.     Thou Shalt Not Steal Other Musicians From An Active Jam.
       ~With time, players move around anyway.

IX.     Thou Shalt Try New Material.
       ~ Original & different tunes are OK occasionally.

X.     Thou Shalt Be Considerate Of Pickers  (and Others).
       ~ Explain when you're rehearsing, not jamming. Help beginners.