Up north if you meet a working boat he normally uses sound signals and you hold the correct number of fingers just above your head. To turn you give the turn signal followed by one or two hoots to say which way on rivers.
Down south where most don't know signals the wife stands at the front and waves to the approaching boat then points as in 'you' followed by which direction we want them to go. If they get it right they get a smile and a wave when passing me (steering) - if they don't one assumes they are Americans.
Boats coming up behind are invited to pass when we think it safe (some don't which we find annoying -h aving them up our arse so to speak. If they accept we indicate which side to pass - normally we choose the metalled side. We like slow overtake some feet away and we pull over to make room then, as they move up we cut to tickover, and keep this on until they are nearly infront sucking us towards them at which point we apply more throttle and steer away until their back end is in front of our front. (The steer away is often made difficult when they start cutting back to centre rather than keeping over when there is still an overlap.) Once they are in front we will be sucked along faster than normal until they get far enough in front for the suck to reduce. Overtaking on narrow shallow canals is the most difficult trick of the lot!