Test if you fulfil the conditions (such as age, nationality, etc.) which entitle you to become an au pair in the Netherlands.
Find out what you need to take into account before leaving your country (what documents you need, etc.)(as an EU citizen, as a non-EU citizen).
What kind of support does the family expect from you? How much holiday are you entitled to? Who pays for your language course?
Do you have insurance coverage abroad? Will your driving licence still be valid? Do you need a contract? What can you do for your safety?