I like it on the continent, riding around the alps a few years ago it
would appear that the the thing to do if you were local was make sure
you had the bike cranked over on a hair pin and go for a comedy wave or
leg wave as you went past
.
I usually nod, wave, leg wave, thumbs up, open hand on bars, or whatever takes my fancy at the time!
Anyway there's not been any discussion on what type of nod, I find sports bike go for the straight forward up and down, slightly down to the right for GS's and adventure types and I go left to right for motos