There are common hand signals used by ground crew for fixed wing aircraft like 'taxi forward', 'spin up engine #1', 'turn right', or 'stop', for example:
At most airports, general helicopter traffic doesn't need to be marshaled, but I'm sure that pilots must be required to at least know some standard signals, in case of some communication issue that would require the use of hand signals.
Do these signals differ for helicopters, and how so? Do helicopter pilots have a different set of signals they must know?