How...

Why, that is really the real question, isn't it ?

HOW ?

Well to begin with, I wouldn't advise anyone to be an au pair without going through an agency... I mean it is so much safer than searching the internet to find a random family you're not even sure about...
It is true that you have to pay a little something to the agency but you are quickly reimbursed with the pocket money and that saves you the trouble of finding a family...
The agency I used is CLC (Club Langue et Civilisation), they do all sorts of things from the two-week trip to the English Riviera with visits and lessons from a year as an au pair to one month in immersion in Australia...! I had to prepare a little application form with some reference letters but nothing really complicated... and the application fee is something around 200€ but if they don't find a family they give it back to you. But really I think it is worth it ! They contacted me a month ago (during the Easter holidays) to say that they had found me a family and voilà !!!

I hope this will help some future au pair... If you have any questions don't hesitate to ask them !!!

=)