The BEST place to start is by contacting the Registrar of Birth Deaths and Marriages in NSW (Ph: 1300 655 236  Web: www.bdm.nsw.gov.au ) where you can apply for a copy of the Death Certificate of the family member you are looking for.  This certificate shows all the details of the deceased at the time of death including the place of burial or cremation.  

You can search online in the Family History section of this site. However, you can only search particular date periods.  Further information on what date periods are covered and details of how to conduct a search can be viewed at:  http://www.bdm.nsw.gov.au/familyHistory/howToSearch.htm

The Society of Australian Genealogists (Ph: 9247 3953   Web: www.sag.org.au ) can also advise on research procedures. 

Cemetery /crematoria offices may also perform register searches, for which a nominal fee may be applicable.

When searching for cemeteries/crematoria in a specific area, try contacting the relevant local council as they usually maintain a list of cemeteries/crematoria for their area.