Once you're comfortable with your ability as a home winemaker, consider contacting wineries and tasting rooms before you visit. Nobody appreciates how much effort winemaking can be more than another winemaker. If they know you'll be coming, you may get tours, barrel tastings and offers not available to tourists. In return, the commercial vintner gets a knowledgeable customer who can talk the language. A year or so ago, a winemaker in Paso Robles invited a couple of us to go behind the tasting room to give our opinion of his still barreled syrah. I've had tasting room people pass the money back across the counter saying "We don't charge winemakers." We've been invited to trade tastings. If you get something free, enjoy the feeling but if it's allowed tip generously and be sure to buy some wine.