My number one tip is to take the day off work for your au pair’s first day in the family… and spend the day giving her an orientation to your home, suburb, and the city, using public transport (preferably without kids).
By the end of this day she should know that you are interested in her well-being, and that you are approachable. Then she will feel safe to come to you when she has questions or when something goes wrong.
And that means you can sort out most problems that arise straight away, prevent home sickness and get her settled in quickly! …what is good for the au pair is also good for you.
PS – Au pairs have been a fantastic solution for us, and a (mostly) very positive experience. 🙂