Here is a guide to newcomers to Australia looking for tips and tricks on how to save money, or newcomers to the OzBargain frame of mind looking to overhaul and tighten their spending, summarised from years of collective OzBargaining wisdom.

PETROL

• [QLD] Check where petrol prices are on the cycle with the RACQ's Fair Fuel app to decide whether to fill up the tank/s now or later: https://play.google.com/store/apps/details?id=au.com.racq.fairFuel
• Double check it, comparing the Brisbane cycle there with the one at the ACCC website: https://www.accc.gov.au/consumers/petrol-and-fuel/petrol-price-cycles-in-major-cities#toc-petrol-prices-in-brisbane
• Find the best prices in the area with the Fuel Map app: https://play.google.com/store/apps/details?id=au.com.fuelmap
• If one of the cheapest is a 7-Eleven, lock it in the app, and fill up in the nearest one: https://play.google.com/store/apps/details?id=au.com.fuel7eleven
• If you're going on a long trip or commute (to Brisbane, say), Google Maps gives ULP91 prices along the way, if you search for petrol with a route on the screen. Then go into the GPS Navigation, and search for petrol again, and it gives how much time the detour to the servo will add to the trip (no point spending a bunch of extra time and money to save a couple of bucks).
• [QLD] Open a free bank account with RACQ (no balance or deposit necessary) to get 4c/L off at Puma servos.
• Sign up with Freedom Fuels (there's one just north of Nambour) to get their 13c/L promotions (but compare it with others around — it's often not worth it).
• Get an OBDII (a bluetooth dongle that connects the phone to the car computer) to check fuel efficiency (in addition to running diagnostics, and monitoring other stats and sensors). No need to go fancy; a cheap $15 one off of eBay or AliExpress will do. Once you start using it, take note — mental or otherwise — of the different fuel efficiencies of the fuel from various servos; often, any price differences are completely obliterated by efficiency differences.
• [QLD] Liberty is generally the cheapest around at any point in time (and the petrol is not too shabby either).

GROCERIES

• Compare unit prices across Coles and Woolworths with the WiseList app: https://play.google.com/store/apps/details?id=com.gy.wiselist
• Also compare to ALDI and IGA with the Frugl app: https://play.google.com/store/apps/details?id=com.frugl.grocery
• Also compare it to Amazon and others (especially cleaning products) with Google Shopping: https://shopping.google.com/
• … and Bing Shopping: https://www.bing.com/shop
• Get a Woolies Mobile plan, that gives 10% off on one store purchase a month (which leads us to the next topic)

MOBILE

• Take advantage of recurrent new customer discounts on prepaid plans, switching between operators when they expire.
• If your phone/s take two (or more) SIMs, get the cheapest Woolies Mobile yearly prepaid plan for calls (for the 10% shopping discount), and use the 2nd SIM slot for data when free 1st month prepaid plans are available — with no worry about migrating numbers, just take the number given; it's only for data — so you don't consume the data from the Woolies plan.

ENTERTAINMENT

• Check Groupon before paying full price for tickets: https://play.google.com/store/apps/details?id=com.groupon

SUPPLEMENTS & COSMETICS

• Use PriceHipster to buy supplements and cosmetics (or anything else really) at Chemist Warehouse when it's truly discounted: https://pricehipster.com/?sortDirection=asc&sortField=priceDiffPercentage&stores=S6K2ld_NN
• If it's not at Chemist Warehouse (it's generally the cheapest, when it's truly discounted, but a lot of stuff isn't there), check iHerb: https://au.iherb.com/
• Also compare it to Amazon (and others), directly or via Google/Bing Shopping.

BOOKS

• Some of the kids books on sale at Kmart and Big W are incredibly cheaper than anywhere else (and are often further discounted too!). Worthy of mention are the $5 hardcover Usborne thick science books, the $5 (sometimes $4!) large, hardcover, glossy Disney/Pixar/Marvel books, the $1.25 glossy, hardcover First Readers series, and the $16 glossy, hardcover, illustrated Hobbit at Kmart.
• Use the library; it's free, efficient, and most don't charge late fees anymore.