Things to check:
Do you have an oldish hot water system. Sometimes they start leaking (invisibly) when they are about to cark it. Get it checked.

Turn off all the taps, go outside read your water meter twice over a couple of hours (when no taps have been turned on/toilet flushed). This might indicate if you have leak somewhere in the pipes (eg under the lawn or under the house)

If you have an old single flush dunny, you can buy a water-saver weight. You pop it into the tube that goes up when you flush - and basically it pushes the tube back down so the toilet only flushes as long as you are holding the button down. That means you can control the amount of water you flush each time.

Check that the outlet/drain hose on your washing machine goes up to the level of the top of the washing machine before it goes down to the drain hole. If just goes straight down, what can happen is it starts siphoning the water out during the rinse&spin cycles and you can use 100s of L of extra water this way.

Hope that helps!