Getting back to the Thread Title - Singaround etiquette ? A singaround is only as good as the people who turn up.
Like Padgett ,a good mate of mine, I've run loads of singarounds.
The best method I found - I had people write their names on a sheet when they entered the room / with instrument or unaccompanied - in addition to the name of their home town. Enough ammo to give them a nice introduction - then give the next singer a nod that they would be "on" after this song.I could also give performers a good idea at what time they would be singing .The list enabled me to avoid the possibility of (say) three unaccompanied girls (or three unaccompanied guys) singing one after another .You could shuffle it around so it made an interesting mix of performers.
As for (say) Christie Moore or June Tabor turning up and being told to wait their turn - I don't think so - dream on - you should be so lucky.