Voting in NSW is different from every other state. Here, the ABC's elections analyst Antony Green explains how "optional preferential" voting works and how it could affect Saturday's result.

These questions were asked as part of the You Ask, We Answer campaign.

Question 1: NSW uses optional preferential voting. Could you provide information on how this works?

Under full preferential voting, which is used at the federal election, voters must number every square.

It means voters invent an order of preference between potentially unknown and what some might call "objectional" candidates.

Under the NSW system of optional preferential, voting the voter only needs to number one square.

The political impact of NSW's voting system shows up when the votes are counted.

Ballot papers that quite literally run out of numbers during the distribution of preferences "exhaust" further preferences.

They are then removed from the count.

It means candidates leading on first preferences are advantaged and second and third-placed candidates are disadvantaged.

Overall, it makes it harder for candidates to win from second place.

For example, at the 2015 NSW election, Labor won three seats from second place on Green preferences — the first time in two decades that the NSW Labor Party had done this.

Yet at federal election under full preferential voting, Labor has won two or three NSW seats at every election from second place on Green preferences.

NSW is the only state to use optional preferential voting. (ABC News: Alex McDonald)

Q: What if there are four candidates in my electorate and I only want to vote for one. If I put a "1" against only my preferred candidate, is that still a valid vote?

Yes. As NSW uses optional preferential voting, you only need to mark one square for a formal vote.

If you don't know the other candidates, or you find them equally objectionable, then you don't have to mark their boxes and show further preferences.

Conversely, you can simply number candidates in the order you want to see them elected: "1" for your first choice, "2" for your second choice and so on.

But if you're voting for a candidate not expected to poll strongly, then the more preferences you give out the more likely your ballot paper will stay live in the count.

It means you'll play a more significant part in determining the final winner.

But be warned; the rules are different at the federal election — in May you'll have to number every square!

The voting rules will be different when Bill Shorten and Scott Morrison square off in May. (ABC News: Nick Haggarty)

Q: How many preferences do I need to mark to make it unlikely my votes will exhaust, but still avoid marking preferences for groups I don't want?

To avoid exhausting your preferences, you should number as many squares as possible — and all the squares if you want to guarantee your vote won't exhaust.

But if you don't number every square, whether your vote exhausts or not will depend on who you preference, not how many preferences you give.

In the end, your vote must choose between the final two candidates in the race to win.

If it doesn't, your vote will exhaust.

Q: If I vote "1" above the line for the Legislative Council (Upper House), can parties direct preferences beyond that?

No, they can't.

Group voting tickets that control between-party preferences were abolished in NSW before the 2003 election.

If you vote "1" for a party, that vote only applies to the candidates of that party — your vote cannot be directed to any other party.

If you want, you can give a "2" for your second choice party and so on and your vote will flow to those other parties.

Under the reformed NSW Legislative Council system, and the new federal Senate system — introduced in 2016 — parties cannot direct preferences to other parties.

The only preferences in the count are those completed by voters themselves.

Q: Will online voting be available for anyone in NSW?

Yes. NSW is the only state that uses online voting — but it is only available if you meet certain criteria.

Q: Do I have to number all the squares in the Legislative Council (Upper House)?

No. If you vote above the line you only have to number one square.

If you want to direct preferences to other parties, you can number "1", "2" and so on.

If you vote below the line, you must number at least 15 squares. You can also number 16 onwards for as many as you like.

You can choose candidates from any column in any order.

There's plenty of choice with 346 candidates.