Heres what i know after recently going through the compliance process on my last car. This is for WA.
Driver side rear view mirror must be flat. Check by placing a flat edge across and see if the image looks curved. It only needs to be slightly convex and it will not pass. Take mirror to any glass/mirror shop and theyl change it in half an hour for about $20.
Belts: My car had the correct standard belts already and was a 2 seater so it didnt require any modification here. To have it done by a RAWS costs around $300-400. You can easily DIY if your okay with cutting trims. (never done it, just seen it) See DRIFTT's post
Tyres: If you're lucky youll get your car with some E or DOT tyres - just look for a circle with an 'E" in it or the word DOT. If not, get some cheap secondhands or swap wheels with a mate.
Placard/Fuel Sticker: you can make these at home - by far the easiest way is to print the design onto thick paper (i like photo) and then just laminate it or you can even use contact if you really need to. They will look at it for about half a second just to see its firmly affixed.
Catalytic Converter: Pretty much have to have one. I had to buy a new one and have it installed, $200. Also, its a good idea to hook up/dummy any pollution gear that should be on the exhaust to avoid getting picked on for that.
Fuel Restrictor: You can buy these from RAWS for around $15-20, and have it installed as cheaply as $30. (Anyone know where to buy them other than RAWS?) A pipe expander tool is inserted into the old neck and when operated expands the neck diameter enough for the new filler to be put in. Its usually siliconed in place. Havn't really heard of any DIY on this, anyone done it themselves?
Intrusion Bars: the biggie. Alot of people dont want the hassle of putting it in themselves, so you can have them fitted for anywhere form $300-400 depending on car. Some models have them factory fitted. But you can do it yourself of course (i like the sound of those rivet-only ones. Sounds easy!)
Thatrs not everything, theres bound to be more that crops up but theyre the big things that needed to be done on mine, hopefully it cleared things up for some.
blacky