I met our vicar last week and was the same in not having a clue what to ask. You will probably find that the vicar will tell you everything without you needing to ask.
Ours started by asking how long we had been together, how we met, about our children ad when we were looking for. She told us about weddings she had done in the past and gave us loads of tips for things like invites and stuff for our theme.

The first meeting is just to get to know you and what you are after really from what she told us. Easier said than done but don't be nervous. xx