I'd start a day in Napa here. It's built around sparkling wine, well organised and good at welcoming people — the right pace for the first tasting of the day. You can also just sit in the garden with a glass.

Domaine Chandon
Where to begin a day in Napa
Good to know
- Mornings are quieter, which is why it works as the first stop.
- Decide who's driving before the first pour.
Photo: Agne27 at en.wikipedia · CC BY-SA 3.0