Here are a few links ...

racingvictoria.net.au/index.php?option=com_content&task=view&id=114&Itemid=16
Check out the PDF's on handicapping policy

racingnsw.com.au/page.asp?parm=han.main
Check out the links on the left - There is a Handicapping policy

waturf.org.au/etc/pics/2007_RBH_Template1.pdf
PDF on ratings vs weights.

racingsa.com.au/racing/pdf/SARatingsTempleplate.pdf
SA Ratings vs weights

risa.com.au/Rating_Based_Info.asp
A good page to check the rating of the horse.

Or you could just search google for "Handicapping policy".

Obviously each state has a different handicapping policy.

Good Luck.