Plenty of talk about this - couple of hints from a person whose done a heap of stoooopid mid summer Australian desert riding (used to live in Alice Springs, NT and Roxby Downs, SA), now live in Perth...
1. Water (already talked about throughout)
2. Stopping in shade once you hit the Nullarbor (stands for No-Trees) is impossible unless you stop at the service stations - use and abuse there air-con!
3. Cotton is usally a no-no when it comes to outdoors, but it is because of this it is ideal for this type of travelling. Cotton will not retain heat once it is wet (hence you don't want it in the snow as it will 'pull' your body heat away), BUT, 40 degrees celsius at 120km/h with a drenched shirt and the jacket slightly open, you will have aircon...
This trick got me and my wife from Pt Pirie too Roxby Downs on a 50c day (just). Wet your shirt (if possible) at the sevice stations along the way - they will ask for a donation for the showers.
4. Oil!! Your Oil cooler is going to be working overtime. I have owned DR650s - love them to death, and they have never failed me any conditions - just keep the oil up and fresh.
5. Don't ride at night. Seems like a good idea, until you see the 6 foot kangaroo or 8 foot camel bounding towards you...
6. DO NOT ride in a short sleeved, shorts, t-shirt or anyhting like that. A - we all know how unsafe it is (riding and sun), and B - you will actually be hotter.
Anyway, have driven/ridden all around that area, so if you need any advice, let me know.
Stop talking, its time for action...