Yeah the interview is all about you. (Actually, that was the first thing they said in the interview: "We would like to get an understanding about _you_")
Things like your memories, experiences, life to date, reasons for wanting to do medicine. I went through rural entry, so they also ask things like why I want to go back to the country and work, where I want to work, how a role model (doctor) has influenced me, roles in the community.
They asked about my work experience, so it would really help if you had some. (any! just something that you can say: I was here and I saw this and it made me think this. If you are rural, i've heard they like you to have done some with a GP too.)
I came out the interview feeling 'weird', and thats about the only way to put it. I had a Co-op interview, and thought that went really well because the interviewers responded in that one.
In the med interview, they basically just sat there, with little face expression. It's also a fairly long interview, about 45-50 mins.
Really, I think the best way to prepare for it would be to simply talk to your parents for a while.
I also didnt do any UMAT preparation, because I thought that defeated the purpose of an 'aptitude' test which tested personal qualities. Unfortunately my UMAT results were not good, and I wouldnt have even got to interview stage if I wasnt a rural person. So each to his own. But if you are a sydney person, and want a first round interview, you will need good UMAT results (along with a high UAI prediction)