maybe a bit mre info would be more helpful [previous unit from uws or another uni?], etc.
the policy is here
http://policies.uws.edu.au/view.current.php?id=00176
the form here
http://pubsites.uws.edu.au/student/forms/Advanced_Standing_0207_web.pdf
for me, i was a previous uws student applying for credit for another uws unit as i transferred into another uws course, so its just a form you fill out [usually the earlier the better and i think the limit was when you enrol, you have to apply in the first semester you study or you cant apply for it later on but you should ask the student centre if there are any revisions]
i also applied from uws to uts, and since its for a different uni, they ask for a unit outline as well, so its pretty straight forward.
if its from tafe, than anything above a cert iv can be used as credit.
however check with student centre, or call the student course line on 1800 897 669 freecall to make sure...or wait for a current uws student...