Good of you to ask. We would like you to bring a valid form of identity (ID card, passport, or driver's license), your debit card, and the details of your references. For your references, we will need the contact details from at least two families for whom you've babysat before.
If you don't have a Dutch, but a different European identity and don't have yet a Dutch bank account number, we also ask for proof of registration with a Dutch municipality. This proof may also be a postal item with your name and address at which you are registered.
If you have an identity from outside Europe, the above is not sufficient. We need a Dutch bank account.