When we planned this trip, we first researched weekly market schedules and planned our visits to some of the towns (e.g., Montepulciano, Cortona, Torrita di Siena) to correspond with the weekly market. These markets are not fancy or gourmet markets, but instead are where locals stock up on their weekly supply of cheese, smoked meats, fish, vegetables, fruit and everything in between. These are the types of markets we enjoy since we can observe how locals do their shopping, the interactions with vendors and just get a feel of people's relationship with food. Our favorite market was Montepulciano's Thursday morning market - we got a bit carried away with ourselves and came home with enough cheese, smoked meats (both Tuscan and Parma proscuitto), tomatoes, rucola and porchetta to keep us fed for an entire week!
Cortona's Saturday market was also nice in that it is located within the historic city walls, but it was quite small so I'd incorporate it as part of a visit but not visit the town solely for the market. As for winery visits, I had contacted the Montepulciano and Montalcino wine associations before we arrived in Tuscany to get a feel for whether we could create our own "wine tours" by putting together several individual visits in the course of a day. Both associations sent extensive lists of wineries with information about tastings, price, availability and contact information (this is also on the websites). When we arrived in Tuscany, we picked up winery maps from these offices and chose a few to visit on our own. Putting together our own "wine tours" worked out great as we could set our schedule in how long we wanted visit each place. We usually called ahead to make sure that the winery was open and that they could take us for a tasting. Our first visit to a family-run winery outside of Montalcino was fantastic, both in terms of the wine and the personality of the owner. For us, being able to meet and talk with the people producing the wine is special as it adds a personal touch and additional story to the wine. In the Montepluciano area, we visited a rather large winery on the edge of the region. Even though the woman who took us through the tastings was not the owner, she had worked there for years and was passionate about wines and answered all of our hundreds of questions. She thought we were newlyweds, and when she found out that we were celebrating our 10th anniversary instead she gave us a small bottle of Vino Nobile di Montepulciano as a gift. At another Montepulciano winery we received information on how to cook rabbit and wild boar hunting techniques. Each winery visit provided us an understanding of the area beyond the wine.