Put a sticker on the dashbord saying: Drive left.Probably the rentalcy already has done that. Be careful at roundabouts, traffic is coming from the right now. Before you start driving in the morning say or think: They are completely mad but traffic is on the left hand side of the road. You'll get used to it soon. Trickiest part is not the driving but crossing the street on foot. We always stand still first and say to each other: Right-left-right instead the "normal" procedure in your own country: look left-right-left. Also you will be confused by the handles on the steering wheel but after you get back to Chicago you will be mistaken first days also haha. And don't bother if you are stepping into the car at the wrong side first. Happens to us all.
By the way, parking in Australia often is with the rear side of the car to the pavement. NEVER drive at dawn, dusk or in the dark, you'll see many cars with bullbars and those bullbars are not for fun here. And like in the USA, most drivers are polite and not to compare with many European drivers. No worries!
Tet