Clothing/Shoes/Weather Gear: you must have a jacket or wind breaker handy in your car of if you are on a bus tour, on your tour bus since the weather in the Napa Valley Area can change drastically any moment from too hot or too cold again due to the micro climates hence the jacket can be handy tool to beat the cold. Also have sung glasses available since the sun glare sometimes in Napa are too much so again, have your favorite Oakley's handy. One more thing, also umbrellas since Napa Valley has occasional drizzles. So that you don;t get wet while doing a wine tasting tour.
Miscellaneous: This is in case you would like to bring home some of the wonderful cheese you can find up in the region. I brought home some Point Reyes Bleu Cheese which is marvelous with red wine. The creaminess of the cheese will make the wine almost taste like ice cream!
Luggage and bags:
If you buy some bottles of wine over the internet, save the packer. Then, bring whatever styrofoam packers you have inside the luggage. If you don't have these, or don't have enough bottle packers at the time of leaving, wrap and tape each bottle inside a plastic grocery bag. Seal the wine as well as possible just in case the cork moves. Then, surround the bottles with dirty laundry and shoes to pad them and keep them from shifting around too much. Glass wine bottles are very durable at the base, but the necks are a potential breakage point. Champagne bottles need extra care. Even so, a case or so of wine (12 bottles) can be safely packed inside a large airline bag destine for check-in as long as they are separated from each other and from the exterior edges of the bag. Then, take the rest as carry-on. Large bottles are valuable, require extra care, and so should be packed by the winery for you. Styrofoam 12 and 6 bottle packers that isolate each bottle can be safely taped and checked-in as luggage.
Clothing/Shoes/Weather Gear: Dress casually, but not cheaply. Many times when working in the tasting room, I found that intoxicated customers, women with low cut or tank tops or men with flowery Hawaiian style shirts and sandals, presented a version of America that other tourists sneered at. From late spring through fall harvest, I recommend khaki shorts, fine fabric short sleeve polo shirts, and casual leather shoes with soles able to trek through a little dirt or over the wet pavement of a cellar room floor. Jewelry and fancy cars are OK. Theft and robbery is rare in the wine country.
Toiletries and Medical Supplies: Bring anti-acids and motion sickness pills. Driving the windy roads of the wine back country will bring the worst out of a slightly inebriated passenger.
Photo Equipment: Bring a wide angle lense for shooting images of winery equipment. Make sure to bring plenty of memory for the digital camera.
Miscellaneous: It helps to have plenty to snack on during busy wine tasting days. The more wine consumed, the more food required to keep it under control. Stop at Oakville Grocery or some other market in the valley to stock up on food for the road. Don't try to be on a diet when in the wine country, but during meals focus on quality, not quantity. Some of the world's best restaurants are in the wine country.
I never travel without my special edition Swiss army knife. Special because it is not a multiple tool but unique with eight efficient corkscrews immediatly operationnal in every emergency situation. Hope you will have yours soon ;-)
Luggage and bags:
Pack what you can. It's good to have a change of clothes before dinner.
Clothing/Shoes/Weather Gear: Comfortable clothes/shoes during the day and nice duds for the evenings.
Photo Equipment: Bring a good camera.
Miscellaneous: A nice shot of Pine Ridge Winery in the Stags Leap District on the east side of the valley. Try the Onyx if you can. Yum!