Home base

Jennifer, I'd suggest that you split your time between at least two places. Otherwise, you will be spending a lot of time on the train.

Verona can be used as a base for Venice and vice-versa. Padua and Vicenza are also easy day trips. Personally, I really like Venice in the evening (as opposed to during the day when it is packed with daytrippers) so I would probably choose to stay in Venice if I could only stay in one.

For Milan and Lake Como, I would probably choose to stay on Lake Como in Varenna; however, from Varenna, it would not be convenient to get to Torino on a day trip.

This is a challenging task, to select a central point that will make sense in terms of cost and time. I don't think any of us have the time to completely figure this out for you.Here's how you would answer the question for yourself to see if this makes more sense than some other way of seeing these:Use this train website http://reiseauskunft.bahn.de/bin/query.exe/en to determine train travel times between various destinations.Use this online map to look at the 230 miles separating Turin (Torino) from Venice (Venezia) http://maps.google.com/maps?hl=en&ie=UTF8&tab=wl. 230 miles is approximately the straight line distance between Turin and Venice, you can draw a line between the two and it extends from the east coast of Italy almost all the way over to the west boundary--that's the area you want to traverse in day trips. Milan is not in the center, Brescia is more in the center. You can use the train schedule website to calculate train travel times from a central point to the furthest points. The train travel times may be longer than you were anticipating. And then there is the daily cost of train fare back and forth. Remember that the times given in the rail website are station to station times only, you have to add for getting to the station in the morning, buying a ticket, waiting for the train, then the station to station times, then getting from the destination station to your first sight by public transportation or walking; and then repeating that process to return to your home base at the end of the day. After your research, you will be able to decide if the extra cost and time is worth it, compared to your next best alternative.

During our Northern Italy portion, we had a hotel in Verona for 6 nights. During one of those nights, we "nigttripped" to Venice, taking only a carry-on with essentials. We saw much of Verona, saw some towns around Lake Garda, as well as seeing Venice during the day and night.
The train stops in Padua on the way to Venice, and we intended to stop there and see some things. But as mentioned in the above post, we didn't have the foresight to factor in the time it would take to get to and from the train stations, the time we'd be waiting for the train, and how long it actually took to travel from Point A to Point B.
So, yeah, I'd pick at least two of those places as a homebase and split your time accordingly. IE, stay a few nights in Venice and daytrip to Padua and Verona and then move on to Milan and daytrip to Turin. Just examples; but I'd recommend splitting up the "homebase" time allotment because you probably don't want to be wasing too much precious time on trains getting back and forth to one homebase.

Keep in mind that during the day cities are filled with daytrippers.In the evening when they leave they are much nicer places to visit.Id stay in different places and enjoy the evnings.