It is not possible to drive around and view every stage, unless your in the zero car.
A lot of locals are happy to find a spot and just watch one stage per day from their spot.
If you have to drive on the Targa stage to get to your viewing spot, you will have to get in there early before the road closes (road closure times should be on the Targa site, or available from the police closer to the event), and you maybe stuck in there for a few hours or 1/2 a day.
If you want to follow the cars around, you want to know where the cars are parked each night. Pick a few spots where there is a access road to get in a watch a stage, then get out and drive to the next one (or the one after that.) When the last car gos through a stage, the first car has probably already completed the stage after that.
It is good to stand on a hairpin and see them all crash, but it's just as good to be at the service place late in the afternoon. A chance to chat to drivers and see bonnets open.
If you pay money, there maybe a VIP viewing tent at some places. This would include a shuttle bus and wine etc.
I was once watching Targa up in the bush with every other bogan and his dog, and this helicopter just landed behind the trees nearby. Minutes later, rich men wearing blue jeans on their day off stumbled out of the bush.