He will need 3 forms of ID i.e. Drivers Licence, Passport, something with address on it etc. He may also need a letter from his employer stating his employment status, hours and pay rate as that will affect the amount he is eligible for.
He will also need bank account details and also a current balance from the bank. They may ask for asset info so good idea to either know that stuff or take with him. If he is renting take tenancy agreement and/or letter from someone he pays rent to stating the amount and frequency for rent assistance as well.
Here is a
WINZ Linky that may help as well.