Common law states the landlord must hand over and maintain the property fit for the purpose for which it was let.
However many lease agreements deal with maintenance of the property differently. It is advisable to ensure you have read the "Maintenance" clause of the lease agreement carefully to ensure you are aware of your obligations and the landlord's obligations.
Most lease agreements provide that the landlord is responsible to maintain the structure of the property and any electrical, plumbing or electrical apparatus which you have not damaged.
Generally the tenant is responsible to maintain the inside of the property "fair wear and tear" excluded. If the property has a garden or pool, it is common that the tenant is responsible to maintain the up keep of the garden or pool. Remember – it is important to refer to your written lease agreement.
The landlord does not have an obligation to fix every item the tenant deems necessary. Items which render the property unfit for the purpose for which they were let, such as no water / electricity, a burst geyser, non-working oven etc. would need to be attended to by the landlord. However the landlord would not be obligated to fix items such as missing internal keys, blown light bulbs and squeaky doors.
Again, it is important to point out that many lease agreements provide for different obligations pertaining to maintenance – read your specific lease agreement to confirm your responsibilities and the landlord's.