You can find accommodation of different types in Sydney.
If you are student, the most recommended is a share house near your school.

The most common for students are:

1 - Share Houses: Houses or apartments shared by students.

Where to find vacancies in Sydney:
-www.easyroommate.com.au (biggest in Australia)
- www.flatmate.com.au (students and australians advertising)
- www.gumtree.com
- www.realestate.com.au (more australians)

2 - Rent a house or Apartment: Rent a house or apartment. It's a good option if you are staying at leat one year in Australia. You can find furnished and unfurnished apartments

Where to find vacancies in Sydney:
- www.realestate.com.au

- Some buildings in the city have their own manager, so you can go and speak to them directly. 

3 - Backpacker, Hostel and Hotels: Good options if you are visiting or staying few weeks in the city. There different options in the city and you can find their websites trough google.