A:   Yell, "Look everybody, free tokes!"

B:   Hit it twice and pass it back.

C:   Ignore him and hope he forgets you're there.

D:   Explain to him that you get tested at work and would really
        love to get in on the action, but just can't.

If you know the guy and are keen on some free smoke, you'll choose B.

If you're absolutely positive that the "musician" is wearing a wire, the guests are all narcs and the whole thing is a set-up in a joint operation between the FBI and the DTF, fabricated to confiscate the sickly plant you've been growing in the closet and prosecute you to the fullest extent of the law, you've probably smoked enough anyway.  Just politely thank him and slink away until you've floated back with the rest of us.  Send us a postcard while you're there.  By the way, thanks for picking C.

If you're leaning a bit toward D: We feel for you man.  Get another job.  Start your own business.  Sell Grit magazine.  Your boss is a schmuck, you're underpaid and unappreciated anyway.  Tonight on your way home, buy a Lotto ticket.  Things will look up for you man, honest.

• The first person to toke determines the direction of rotation.  Default is clockwise. If you can't remember which direction a clock runs, you've had enough anyway and should sit down for a bit.
• NEVER EVER reverse the rotation.
• If you wander off and get missed, you're shitouttaluck.  You snooze you lose.  Get back in there, but don't double-toke.
• No Bogarting:  Don't toke like you're siphoning gas or working your way up the political ladder.  Toking for broke is rude. I don't care if it is your weed, have some damn courtesy.  Puff, puff, pass is the general rule.
• Default Bong Rule is one bowl per turn because anyone with a lick of sense packs a bong like a one-hitter--it keeps your precious ganja from burning away while you're holding your hit or passing the bong.
• Anyone caught "Bogarting" is subject to public ridicule concurrent to and after the offence.
• Whoever brought the weed packs the bowls unless he/she chooses to delegate the honour.
• Unless you're of the perpetually uncouth persuasion, you never ever forget to remove the seeds before rolling/packing/smoking.  Seeds are among the most disgusting bits of matter to set ablaze and inhale.  They are prone to spontaneous explosion which is a safety hazard and severe buzzkill.
• Blowing into a pipe/bong is a no-no.  It lets us all know you've had more than enough.  Go find something to do, Sport.  For starters, pick up all the weed you  blew onto the linoleum.  People have been excommunicated from smoking circles for such an offence.
• Dropping the weed onto a carpet or any upholstered furnishing is also punishable by immediate ostracism and public humiliation.  One can only hope that the weed is his, the carpet/furniture is his and nobody saw it happen.
• The host always provides whatever munchie food is immediately available.  If consensus decides upon a procurement of pizza, the person pro-offering the pot is exempt from the purchase price.
• Never insult the quality of someone's weed.
• Always say thank you.
• He who hath provided the weed also picks the music.  Sharing herb makes you Big Kahuna.  Use your powers wisely.  It is a formidable position to hold.  Use wisdom and conviction, and you will be forever esteemed by your compadrés.