By far the best places to stay when visiting Italy are the 'Agriturismo' in terms of price and quality - and the personal touch. These are houses in the countryside, not always far from the city, where the owners produce some or all of the food / wine they serve you! You can eat really good, genuine food without moving from the house, after a long day of touring and visiting! This also means you can enjoy a glass of local wine without having to drive.
Bed and Breakfasts are not exactly the same in Italy as they are, for example, in England. The breakfast is often quite small, with biscuits and coffee, so don't expect a cooked, full breakfast here.
Hotels: there are a lot of hotels in Italy, so ideally book a hotel which has photos of the interiors on the website. Avoid 2 star hotels generally, unless price is a major issue - in which case a Youth Hostel would be a better option, where you can get a bed and breakfast for €16 in downtown Rome! You can also eat in most of them, but eating out is the better option, they don't normally do pizza.
For luxury hotels, we recommend the Italian website italianday.com, because they have the fullest list of hotels, contains good suggestions, top restaurants and they know what luxury is!
Rome, Florence and Venice are the most visited towns in Italy. Bologna is less visited but beautiful and Umbria is a good alternative to Tuscany - where you can rent fabulous villas at reasonable prices. The villas in Tuscany are also fabulous, but more expensive.