There are a number of factors in answering your questions. Will you have a car? Do you want to taste or tour a winery? What kind of wine are you interested in? Have you tried using this forum's "search" function?

There have been numerous discussions of your topic--try "Chianti wine tasting", "Brunello wine tasting". Verrazano and Vignamaggio get good marks from people who make arrangements to tour near Greve (I have not been). I always recommend Le Cantine in Greve--a wine store/museum with enomatic machines that allow you to taste up to 150 different wines and some olive oils.

Most wineries will offer you some form of tasting if you can contact them in advance but they will rarely have tasting rooms staffed similar to California/ US wineries. I've had very pleasant experiences in the Montalcino and Chianti area, but always with some prior notice.
Good luck and Cin Cin! Paul

We were out walking near San Gimignano when a woman in a car pulled up on the track and, instead of telling us to get off her land, asked us if we would like to do some wine tasting. Although it was only about 10.30am we said "yes please", and followed her to a small winery. We had a very enjoyable tasting and bought lots of wine, which was delivered to our hotel by the time we returned.

We spent a week in Tuscany. The first half in the Chianti region and the second in Southern Tuscany near Montalcino and Montepulciano.

For the Chianti area, I contacted numerous wineries via their website or email. (I've collected a list of wineries to visit from the Fodor's boards, as well as the ITC Italian Wine book.) I've received immediate responses from everyone I contacted. - all very friendly. It was all a matter of scheduling. We traveled off season, and therefore tours were limited. Yet on one tour (Fonterutoli) we were the only people on the tour. It was awkward but we had the full tour. So much history! Be aware of your appointment times and distances from each other. We were forced to cancel an appointment because the distance was further than we expected. (Another appointment held us up)

As for Southern Tuscany... which is a must, of course! I did not make arrangements ahead of time. We were staying at a nice hotel/inn and I had assumed I'd have help on this matter. I also like to get personal recommendations when we go wine tasting. We enjoy unknown wineries off the beaten track. It didn't work out. TWe ended up only visited 2 wineries. These were the well known wineries — Banfi and Poggio Antico. They were still great visits. When we arrived at Poggio Antico, the friendly guide (an expat) was actually giving a tour. It was perfect timing because the next step was the tasting. She later recommended her favorite wineries. Which we weren't able to get to, but still kept it in mind. We ended up tasting in the hilltown of Montalcino.

As for Montepulciano, we stayed within the city. Numerous places.

Overall, it's easy to drop by the large wineries. These are most likely the wineries listed in guidebooks. Do not assume you can make arrangements at a Tourists office. There are very few that do and you need to watch out for those siesta hours!

Thank you for your advice.

Yes we will have a car. We would mostly want to taste but a bit of touring would be interesting.

I didn't think to search so specifically on these boards (duh!) I had typed in "italy wine tasting" and didn't see much. I will certainly give those other subjects a try, macanimals.

We do have a couple of wine books - I will pull them out and start google-ing too!

Fonterutoli is the most delightful historic hamlet not very far from Siena. It has the most charming old stone buildings and all of the gutters and downpipes are made from copper. It has original Roman roads through the village and a beautiful home and gardens of the Mazzei family who have been there since 1435. A tour of all of these things are included in the tasting so it is really worthwhile with all the history of the village included. AND THE WINES AREN'T BAD EITHER!! I bought a couple of Classic Chianti's but decided to drink them so I wouldn't have to carry them with me to Positano. (Well that was my excuse!) Also the drive from Siena to Fonterutoli is very spectacular. We actually stayed on the vineyard at Il Caggio with rolling vineyards and olive groves and spectacular scenery. Go there and enjoy.