I can only echo what previous posters have said about networking.
In my case I made contact with all the offshore operators local(ish) to me and after the initial knock backs I stayed im touch with one person frm each operator (chief pilot, hr manager, line pilot etc)
After about 18 months this (prob coz they were so sick of me pestering them) I was called for an interview and subsequently offered a job with an operator which operates EC225's and S76's with no prior offshore experience of my own.
So for me it was a mix of luck and just making as many contacts as I could.
Cheers
garfs