Most travelers do not need a visa but unless you come from another european state you would need a  passport .

Flying is the easier way to enter Sardinia. Most tourists come in through Elmas airport in Cagliari, but some international charter companies also use Alghero or Olbia airports.

You might also want to give a look to boat transportation althought it takes from 12 to 24 hours from the mainland to the island.

Public transportation is not very efficient but cheap and easy. If you plan to move around a lot consider renting a car.

The quality of hotels in Sardinia ranges from excellent to bad. To help you avoid the bad ones, you might want to contact a local tour operator as Hosteras.it who provides a complete guide of available hotels, motels and bed-and-breakfasts all over Sardinia.