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The key distinction in managing a rental property in tax terms is knowing the difference between expenses that can be deducted immediately (such as interest on the loan used to buy the property, maintenance, repairs and lease preparation costs) and those which have to be spread out over a number of years (such as major improvements or capital works). While the latter can be claimed immediately if they're less than $100, that seems pretty unlikely. And don't assume that just because you've spent money as part of an investment purchase, it qualifies as a deduction. A common mistake for new rental property owners is to assume that their conveyancing costs are immediately deductible -- they're not.
What can't you claim? If you have a loan largely used to purchase an investment property but you've used part of that money for other purposes like buying a car, you should exclude the interest associated with that secondary purchase. You also can't claim the costs of travelling to inspect or manage the property if the main purpose of that trip is a personal holiday. (If you own a holiday home which is also rented to others, you need to apportion costs to reflect that usage.)
The ATO link below contains links to lots more rental property advice and outlines of the different types of deductions available. As ever, you may need specific advice relating to your particular circumstances, but knowing the basic rules ensures that you (or your advisers) are less likely to make a mistake.
Investment essentials [ATO]