Monash offers a number of elective subjects where you can do practical training AND get credits for it - Professional Practice, Advanced Professional Practice and I think there's one specifically for family law as well - if you go to the Law FAQ thread in my signature I think I linked to some of these subjects so you can have a read of what it says in the handbook.
You could also volunteer at community legal centres - there's a few near Monash (Springvale Legal Service is one) but they are EXTREMELY competitive since everyone wants the experience.
I don't know about volunteering at law firms but I'm sure they'd be happy to take slave labour, lol. If you're lucky you might even find a part time paid research assistant type job at a law firm (again, highly competitive) during uni. It's not great pay ($20-$25 an hour usually) but it's experience.
I think most places (whether law firm or community centres) won't want to take you until after 3rd year. Before then you won't have enough knowledge of substantive law to be of any help really, and you'd probably just end up doing secretarial/administrative work.
After you graduate it is compulsory to do a year (I think) of legal training before you can actually practice as a lawyer