It depends what you are looking for from your trip. I'm lucky enough to have been there lots of times, and love the country.
Milan and the north is quite cosmopolitan, and it's not too far to go to see the Italian lakes. Como is especially beautiful. If you like opera La Scala is a wonderful venue, as is Verona.
My favourite city in Italy has to be Florence. It's the most beautiful city I've ever been to. We stayed in an apartment right in the heart of the city, within walking distance to the fantastic Duomo. Even if you aren't an art lover a visit to the Uffizi is a must, and you can buy tickets in advance online, which saves you having to queue. The Tuscan countryside is easily accesible from Florence.
Rome is mad. Loud noisey, and a totally different feel to the northern cities. The history and architecture is wonderful. Although like any capital city it can be expensive, you can have a wonderful time and save money by doing it all with a guide bought before you go.
If you fancy seeing a different side to Italy away from the tourist trail, get down to Puglia, in the heel of Italy. Life is much more relaxed, the people are very friendly, and the Trullis, sort of Puglian oast houses, are amazing.
The food of course is wonderful, and there are restaurants to suit most budgets. Clothing is less expensive than here, and you can bag a stylish bargain or two.
Great deals for flight and accomodation can be found online. Train tickets and car deals can also be booked this way, and the public transport system throughout the country is first class.
Next summer I'm hopefully going to Liguria on the north east coast.
I hope you have a wonderful time.