Raised hand: ‘want to talk’
Point at someone with both index fingers, alternating (this gesture is a bit hard to describe, it’s like if you were making guns with your hands and shooting at them, with a lot for recoil): ‘direct response’. You can usually tell how urgent they think the point is by how hard they’re moving their hands/how close they are to the edge of their seat, etc.
Triangle with index finger and thumb of both hands: ‘process point / meta-communication’
Twinkles (wiggling fingers of both hands): when unprompted, ‘I agree/like what you just said’, or it can be used to answer questions on a scale based on the position of the hands → high twinkles is positive/I agree/a lot, low twinkles is negative/disagree/a little, middle is ‘meh’
The wiki article on occupy movement hand signals has pictures and good descriptions of these signals, and others.
At one organization I work with we mostly have a ‘wait’ culture, and it is socially enforced, since we have recognized that many of our members are ‘waiters’ and will not speak if interrupters do not give them a chance.
With more than 3-4 people we use several hand signals to facilitate conversation. We have the usual raised hand to speak next, but we also have a separate gesture for ‘I have a direct response to what you just said’, which takes priority over raised hands. It works as a ‘soft interrupt’, and it is up to the current speaker to let the interrupter speak. The interrupter can usually communicate how urgent/important they think their interruption is through body language. Now when the conversation gets heated we have people gesturing hard at each other instead of shouting. I think it does improve the quality of conversations.
We also have a gesture for ‘I agree with this’, and a gesture for meta-communication. The ‘meta’ gesture has absolute priority and is used for things like bringing the conversation back on tracks at meetings, or to remind people to follow the conversation rules. We usually don’t need a designated moderator as we moderate each other and enforce the norms with the ‘meta’ signal’.
I’ve found this system improves the quality and productivity of our group conversations and I’ve found myself getting frustrated in other groups who don’t use hand signals.