I get asked this question alot, so I have started asking Captain's and First Officers on the Superyachts I visit what they would look for in a crew member/deck hand and how they generally find staff; this is what they have told me:-
Crew Agency - JF recruiting has been pointed out by a few Captain's as a good agency to register with as it is free of charge for you to register your details and they are vastly cheaper than many others for the Yachts which therefore means they get alot of business.
'Walk the dock' - if you are wanting a job, then walking the dock can be the best way, rather than signing up with a crew agency that then charges the Yacht for your employment. If you are going to this then there are a few things you should consider:
Areas you might wish to consider visiting for this are:
Palma, Mallorca - Club de Mar, Astilleros de Mallorca, STP shipyard, Puerto Portals etc
Golfe Juan, France
When should you go?
March, April, May are the best times when alot of Superyachts are in Shipyards/marinas having works done and preparing for their charter season.
Certificates / Qualifications:
STCW 95 is the minimum qualification you will require for anyone to employ you onboard
Other qualifications that may help you are:
Keep an eye out on Dockwalk for job opportunities