From San Francisco via the Golden Gate Bridge:

1) Take Interstate Highway 101 North to the Mission Street exit and then through downtown San Francisco by turning left onto Van Ness. Follow Van Ness and you will be almost forced to turn left onto Lombard. Lombard will take you right onto the bridge.
Or
2) Take Interstate Highway 101 North to Highway 280 West (watch for the signs to San Bruno). 280 will turn into Highway 380 and then into Highway 1 (also named 19th Street). Follow 19th Street and it will lead you right onto the bridge. A landmark here is that you have to go through the McArthur tunnel before you reach the bridge.

From the Golden Gate Bridge:
Highway 101 North until the exit for Highway 37 (exit 460A). The signs will indicate Napa/Sonoma. Highway 37 East to Highway 121/12. You will be approaching Infineon Raceway on the left which will be a lighted intersection where you turn left onto 121/12. 121/12 North until Highway 12 splits off to the right. If you go straight at this intersection you will be on Highway 116 headed for Petaluma; this is incorrect. Highway 12 east until a tee in the road at Highway 29. Turn left and take Highway 29 north to the Oakville Crossroad. Turn right and go to the tee. Turn left at the tee onto the Silverado Trail. Go north on the Trail until Deer Park Road. Turn right and go about 3.5 miles to White Cottage Road. White Cottage is marked with a green road sign before the turn. You can only turn left onto White Cottage. Take this 1.5 miles to the winery. The entrance is on the left and you will see the sign before you reach the turn-in.