For your accommodation needs, upon arrival to Italy, visit the Ente Regionale per il diritto allo Studio universitario (Regional organization for the rights of university students) or the Ente Provinciale del Turismo (syndicate of the province).
Apartments, especially in the big cities, are very expensive. Many Italians instead choose to share places. To find a shared apartment, you can visit a real estate office, look at advertisements in the newspaper or read the bulletin boards on campus or in the libraries.
Check out the Studenti website which places advertisements for students looking for accommodation.
