There is no better place to start researching your soldier than the Australian War Memorial’s website.

If he served overseas he will be found on the Embarkation Rolls.

1. Go to : http://www.awm.gov.au/nominalrolls/ww1/embarkation/

2. Type in his name, and you will be presented with a list of those with that name that served.

3. Find “your” man and click on his name.

You will then be given his details AT EMBARKATION – his service number, age, rank, unit, ship, date and place of embarkation.
NB. There is a valuable link to the digitized version of the Embarkation Roll that will also give his Trade, Next of Kin (and their address), Date and Place of Enlistment, and Religion.

4. If “your” soldier died overseas, he will also be found on the AWM’s Roll of Honour:
http://www.awm.gov.au/roh/

This is valuable as it provides further details such as date of death, next of kin, cemetery or memorial, and a digitized copy of a circular returned by the Next of Kin to the War Memorial that can provide remarkable insights into your soldier’s pre-war life eg. Schooling

The Commonwealth War Graves Commission website's "Debt of Honour" Register will show the exact place of burial or commemoration : http://www.cwgc.org  (It also has photos of each Cemetery and Memorial.)

5. Next, armed with your man’s unit and service number, you may find his entire service record digitized at the National Archives of Australia website:
http://www.naa.gov.au/the_collection/defence/conflicts/ww1/ww1.html

This should provide original documents from enlistment, medicals, award citations, and a record from which you can trace your man’s movements from enlistment, through the war, to discharge and after if he was lucky.

6. If your man was a member of the 39th. Battalion AIF the consolidated Embarkation Rolls are searchable here : The Men 

7. Check the Links page for other useful resources.