Wow, getting an ABN as a sole-trader was much easier than I expected. I have this left-over memory of having to scramble for random and bizarre information from when I applied for Renaissance Fence's ABN - but I guess it was because I didn't know all of Rick's vital statistics then.
For future reference, apply online here If you are on a mozilla-browser (eg Firefox) - ignore their "we don't support your browser" warnings. Their "you don't have scripting turned on" warning is equally useless. Luckily they have provided a "continue if you are sure" link or I'd get really mad.
Their password security is borken - 5-8 characters only? They actually stop you from typing a longer password! They have some other wierd restrictions too (eg letters can't be doubled... but I found out that digits can); that don't *really* add that much more security to them... <sigh>
Their html forms are ugly-as - requiring only a bit of human eyeballing to tell them that, for eg, date field do not need to stretch across half the page - whereas an email field would probably do better with more than only ten characters visible.
Otherwise it's all pretty straightforward. You can even save and return to it later if you need to go find your TFN (I had that handy, this time around).