We are staying several days in Montalcino and will visit Siena for the day. Not to miss anything and understand what we are viewing, we prefer an English guided tour. I visited the Siena tourist website, but no info on this. Does anyone know particulars? Also, can you recommend a casual lunch restaurant. We usually have our larger meal in the evening.

Do you really feel you need a tour? Montalcino isn't very big. You could take the bus on your own (about 3€ one way). I would take a morning bus, tour around, have lunch and get the afternoon bus back. There was a bit of a gap in time between the afternoon bus and early evening of about 3-4 hours. If you want wine, snacks and views, I like this wine bar.
http://www.osticcio.com/index.htm

Grappolo Blu used to get good reviews for meals.
http://www.montalcinoitaly.com/taverna.htm

I was referring to guided tours of Siena. Sorry about the misunderstanding.

Opps! Sorry, I misread the post, but you can easily hop a bus to Siena for the day. Just make sure you know when the last return bus leaves. The bus will either drop at the train station where you can hop the local bus to the center (just a few minutes ride) or it will drop at Piazza Gramsci where you can walk. There is a ticket office under Piazza Gramsci (with luggage storage) where you could get a map or there is the tourist office in the campo. I'm sure they will have tours you can book. Siena historical center is pretty compact.

This site lists any variety of tours in English for the area.
http://www.guidesiena.it/en/index.html

Go to toursbyroberto.com and see if he is doing tours in Siena. I really do not think you need a tour--just read a good guide book and have lunch on Il Campo just for the experience. Plan to spend an hour at the fabulous Duomo and do not miss the library Piccilomini at the end.

There's also a tourist office in Montalcino. I'm sure they offer tours to Siena.

Here's another idea. Not as personal as a guide but I used audio guides downloaded on to my mp3 player, a Zen Mosaic, when we visited Torino, Pavia, Padova, Vigevano this summer. Each had walking maps to follow along with. Siena has an audio guide download, also. http://tinyurl.com/mh5fvp

ttt