Firstly make sure you’re claiming Family Tax Benefit (FTB). If you are not receiving fortnightly payments from Centrelink or the Family Assistance Office you may be able to lodge an FTB claim with your tax return. FTB can amount to quite substantial sums.
Secondly make sure you’re claiming any available tax offsets, such as medical expenses tax offset, dependant spouse tax offset (cannot claim this if you receive FTB), super contributions on behalf of spouse tax offset, child care tax offset etc. Read the TaxPack to see what other tax offset are available.
Thirdly make sure you claim a concessional Medicare Levy rate. A family with 3 children will get a reduction in the Medicare Levy where combined income is under $42,387. Refer item M1 in TaxPack.
Finally, don’t forget about your deductions. Things such as union fees, home laundry of uniform, stationery, your computer and internet access, your mobile phone, donations over $2 and travel MAY be deductible. Refer to TaxPack and make sure you keep your records in order.
A good tax agent could help you too. I empathise the word good, as some tax agents may not suggest these things without you asking them, whereas a good tax agent should be able to suggest these things first.