There are a few requirements if you want to extend your visa for a third year. The first requirement is that you hold, or have previously held, a Working Holiday Maker visa (subclass 417 or subclass 462). Another important requirement for citizens of most countries is that you complete six months of 'specified work' during your second year to qualify.
Specified work refers to employment completed in an industry and location outlined by the Australian Government Department of Home Affairs. Because specified work takes place outside of Australia's major cities, it's often called 'farm work' or 'regional work.' Popular second and third-year visa jobs including fruit picking and packing, fishing, pearling and construction.
The work that counts toward your required six months of specified work depends on your visa, so check the Home Affairs website to find out more.