As what most have said above, Call ahead about fuel to make sure it will be available and confirm their methods of payment, some will tell you they have Carnet but you may find its Inop so carrying a bit of cash with you at all times is something I highly recommend and make sure you have a Credit Card with plenty of Credit available just incase!! And never rely on a single fuelling point, try and work out 2 you can get to incase the other one fails, never happened to me but i'd hate to be stuck somewhere waiting for the next load of fuel to come in cause someone buggered up!!
Shell Carnet cards are next to useless, a lot of their Bowsers have either been removed or now no longer use Carnet and use Credit Card instead. Be VERY CAREFUL with using your CC, they require you to do whats called an "Auth". Basically, it will ask you to input a max amount (In Dollars) first, it will then check that amount is available on your Credit Card and then freeze that amount for several days, when its unfrozen the amount unused will be made available to you again. Basically if you decide to put way more on the Auth than your going to use and do it a few times then you'll find your Credit Card unusable for sometime, also i'm not sure how well they work with Debit Mastercards, i've done Auths on those cards myself before and they seem to work but just be sure first
Carry plenty of Water just incase, make sure you have an ELT and if possible get your hands on an EPIRB as well with GPS tracking, a lot of schools will have them and should most happily let you use one for your trip or someone in the area may well have one they'd be happy to lend you, lifesaver if the ELT should stop working.
Keep one bag with most essentials and an overnight bag as well, this way if you are in the unfortunate position of having to walk some distance into town you won't have to lug the entire thing with you, its caught me out a couple of times! As someone else said, call the hotel/motel/accommodation ahead of time and they'll usually be more than happy to help you out and come get you and do be sure to check they are able to pick you up as well.
Quick tip if you find yourself unable to get reception to pull weather and are fortunate enough to be in a place with a BOM Office (Eg, Tennant Creek, Giles etc...) the people staffing them are usually more than happy to let you use their computers and do a quick print out of the weather you need, once again, its helped me twice in the past so always good to know, just knock, explain your situation and ask politely!
Oh, and this may seem silly but... carry snacks, you just never know where your gonna get stuck overnight and be without something for dinner!! Keep muesli bars or some trail mix type stuff somewhere out of direct sunlight!!