To qualify for a skilled visa subclass 189 you firstly need to nominate an occupation on the Medium and Long-term Strategic Skills List (MLTSSL)
if with State Nomination or Employer nomination the occupations are extended to the Combined list of eligible skilled occupations which includes the list Short-term Skilled Occupation List (STSOL) and Medium and Long-term Strategic Skills List (MLTSSL)
https://www.border.gov.au/Trav/Work/Work/Skills-assessment-and-assessing-authorities/skilled-occupations-lists/combined-stsol-mltssl . There are Caveats that apply to certain occupations for certain visas.
In all cases you need to have the appropriate skills and this may require a tertiary qualification and/or additional skilled experience in some cases too.
Following the visa reform changes announced by the Australian Government in April 2017, we anticipate further changes on 1 July to the Short-Term Strategic Skills List (STSSL) and Medium and Long-term Strategic Skills List (MLTSSL). We recommend that you take this into consideration when lodging any new applications.