Ok I have just been through this myself, so here's my offering.
I only applied for Charles Sturt as I didn't want to live in Sydney, so I know mostly about that application process, though as a rough outline for Sydney you have to sit the multiple choice STAT, as well as fill in a thingy saying what animal experience you have had. You also need to score very higlhy in both STAT and ATAR to be competitive as it is a very very very competitive course to get into. Sydney has a greater focus on small animals (those usually encountered in city clinics) however does do some large animal stuff (predominantly horses and some farm animal stuff). Charles sturt does do small animal stuff, however there is a greater focus on large animals than the sydney course as it is expected that students will graduate and then go out into rural mixed practice. Cut off for csu is 90 for city students, 85 for rural students.
Now, Charles Sturt:
In August the questionnaire is put on the csu website. It has a number of sections. You have to list all your experiences with animals such as working on a farm or doing work experience at vet hospitals or zoos. You also have to write a short essay type thing - you will be given three topics, the ones I had were the use of animals in the lab, brumby population control and intensive pig farming. You need to discuss in this essay the practical and philosophical issues surrounding your chosen topic. You then have to write a letter to the head of the school saying why you think you should be selected for the course. You also have to print our a 'predicted score letter' which you give to your principal to fill in and return to the university. The predicted score letter and your questionnaire have to be in by the 30th september.
In late october/early november you will get an email which says if you have been offered an interview. (for the sake of the explanation let's assume you get an offer for an interview"). these are usually conducted in wagga in late november/early december. Basically you are given a time, you show up about half an hour before it, and you sit in a big room with desks and vet magazines with other people being interviewed. They call you out and you get taken into a little room and you get to see the questions you will be asked and have a think about what you are going to say. Then you have your interview. There are 3 people - I had the head of the school, a senior lecturer and a local vet. The questions I was asked were along the lines of:
1) Why do you want to study vet science?
2) Why at Charles Sturt?
3) What qualities do you think are important in a rural vet?
4) What problems can you forsee a new graduate might have in their first job in a rural practice (think, isolation so reduced access to facilities as well as not knowing anyone. Look at personal and professional i.e. being a long way from where conferences are held so harder to keep up to date with current techniques)
5) What are your opinions on intensive farming?
6) Climate change is a growing problem. how can rural vets help? (a bit of a tricky question as it can be interperuted in two different ways, ie in Preventing, or in helping farmers to manage the changes such as during drought. If you take the first option, there has been some research into changing diets of cattle to reduce their methane output, but the second interpretation is far easier, such as nutrition during drought, advising farmers on when and which cattle to cull, allowing farmers to pay when they can when times are tough and so on)
After that you basically get a yay or nay when early january round offers come out.
very important though - you MUST put charles sturt as your first preference if you want to go there, as most of the places are filled in early january round rather than in main round, and if you don't have it as your first preference you won't be considered for places until the main round of offers.
Oh, and also try and get as much work experience at as many places as you can (no matter if you are trying for wagga or sydney) as having more experience will ALWAYS put you ahead of others, even if you score slightly lower! Try to get experience with cows, sheep, horses, wildlife, cats, dogs etc... and anything else you can think of. The more the better! Also I learned it is far easier to get it out of the way as much as you can earlier in the year as you don't want to be running around doing that when you should be studying for exams! (I didn't do it that way and regretted not getting more experience than I did, however i have been working at my local vets for about 3 years so I suppose that counted for something lol). Oh, and get REFERENCES from each and every person you do work experience with. It sure beats trying to chase everyone up to give you one, as you will need one to support each experience in your application questionnaires.
Anyhows hope the above was of some use to you. Good luck with your HSC, and if you need any help at all don't hesitate to send me a message on here - I am more than happy to help!