Senate Ranking System
This system is designed to rank those parties that you have no opinion on, or know nothing about in the senate. At the moment, it only contains the NSW senate information.
The principle is that the parties who give preferences to the parties you prefer are more likely to have similar views and policies to the parties of which you approve. Conversely, if a party approves of a party that you disapprove of, or disapproves of a party you approve of, they are less likely to be a party to which you want to give votes.
It works by asking you to select a small number of parties that you do have an opinion on, and ranking these. It then matches this up with the ticket information on each of the parties. The information for this system was taken from the ABC's election website.
If you vote above the line in the senate, you give the party you vote for your primary vote, but you also give them the right to distribute your preferences as they see fit. However, in the senate, a candidate need only gain a "quota" to become elected (around 14%), rather than an outright majority as in the House. For this reason, your preferences in the Senate actually mean more than they do in the House. To my mind, this means you should really vote "below the line", in order to direct your preferences how you want. But because the prospect of voting below the line is daunting (in NSW, for example, there are 78 candidates), around 95% of people vote "above the line".
For more information about how the senate voting system works, I highly recommend Antony Green's Senate Voting System Guide.
Select some parties of which you approve and disapprove
Express opinions on as many parties as you like, but remember, the idea of the system is to give you information on the parties on which you have no opinion, so giving an opinion on every party defeats the purpose. Giving no opinion on any party gives the system no information, so the ordering it produces is arbitrary.