Well, this looks like a big trip! From an Australian perspective, don't even think about cycling out of Sydney, the traffic is a nightmare and it's a dog eat dog world. Best to get to the start of the first major road by train/bus, depending on which route you are taking. "The coast route" means many things, but I take it you're planing to ride south from Sydney to Melbourne, then around the coast to Adelaide then across the Nullaboor. Some simple things - ALWAYS wear a helmet. In some states it is complusory anyway, and it makes good sense given our drivers. Lights are a must as well. Across the Nullaboor can be tricky given the huge "road trains". Not done it but have read the stories. Having said this, there are plently of people who have had wonderful rides. As mentioned in other replies, you really need to have a good look at the time of year if you want to avoid 40c temps. Let me know if/when you are plannign the Sydney bit and I can give you some more detailled advice.