How to avoid dodgy operators? Self discipline mainly. Just don't jeopardise your life for an hour or two's flight. Have you joined the AFAP? You should. Know the award and what you're entitled to and don't be afraid to point it out to your employer if he/she's deviating wildly from it. Your contract/agreement ought to be respected and you need to respect your employer too.
How to be employable?
Dangerous goods certificate. First aid certificate. If you're heading off to the touristy areas (Broome, Kununurra, Kakadu etc), if you can get minibus etc on your driver's licence. If you can get some experience doing 50-100 hourlies, do that.