My wife and I just spent 10 days in Northern Italy. We flew in and out of Milan, but spent all of our time in the Dolomites( Ortisei) and the Verona/Lake Garda area.
Our first 3 nights were spent in Ortisei which is about 3.5 hrs from Milan by Car. It's an hour to the North East of Bolzano Italy, just off the A22. Being in the Dolotmites, the main summer activity is hiking on the many trails and stopping to have food and drinks at the many huts that are located throughout the mountains. Right around Ortisei most of the hiking is done through the ski area, and there are gondolas and lifts to open to get up the mountains. It did rain one day, so we drove to Bolzano in the hope of seeing the "ice man" exhibit at the archeology museum, however the line was insanely long due to everyone coming down from the mountain towns. Ortisei was a great start to our trip as it was relatively peaceful and relaxing. Lots of spas in the town.
The rest of our trip was spent in the Verona area. We rented an apartment not far from the Arena and a convenient 24-hr parking garage.
We spent about 3 days driving around various villages along the shores of Lake Garda. We rented a boat in Sirmione and traveled around the lake for a couple of hours. There are many castle and roman ruins along the lake and having the boat provided an awesome way to see them from the water. There are beaches along the lake but few are actually sand. In fact all the ones we were at were small gravel. Other activities included wine tasting at Fraccaroli Vinyards in the Lugana Appellation, walking around the town of Lazise, and just taking in the amazing views with the mountains surrounding the lake. The whole area is an easy 20-30 minute drive from Verona. I would have gone to the lake everyday if my wife would have allowed it. We saw only a fraction of the towns and sights surrounding the lake.
In Verona itself we spent several days seeing the various sights and churches. We went to an opera in the old Roman Arena one night, which was an amazing experience. I don't really like opera but seeing it in the Arena made it worthwhile. All of the churches in Verona are amazing and stand up at the top of most of the churches I have seen in Europe. We did see the "Juliet House" but I'd prefer not to waste time discussing how I stood in a courtyard to observe a balcony in which it's only claim to fame is that it's in a fictional story. Verona itself could consume 2-3 days of sightseeing alone.
We did take the train to Venice for the day. Originally we had planned on spending two nights in Venice, but based on advice from my Italian friend from Verona and our apartment land lord we chose to just take the train over for the day. It turned out to be the best decision we made. First our apartment in Verona cost about the cost of our hotel in Venice, and second Venice was a bit of a disappointment. After a trip where we encountered few large tourist groups, as expected Venice was packed with the large groups. In addition the dirtiness of Venice was a bit off putting. Especially after having spent most of our time in areas that were well taken care of. It's hard to appreciate the canals with trash floating everywhere. The train ride from Verona is about 1.5 hrs, and there are trains every hour. In total for two it cost 34 euros round trip.