If you are traveling across length of Italy, it is better to know about Trenitalia.com or you may end up not getting seats at required time.
1. You will see an extensive list of trains including both Freccia (Fast - speed) trains or regional trains. Freccia naturally costs more than regional ones but usually take 3-4 hours lesser than the other ones. You can choose as per your convenience.
2. Take note of the station names as cities are pronounced differently in Italy - Venice as Venezia, Florence as Firenze, Rome as Roma etc.
3. Do not forget to validate your tickets before boarding trains or it may cost you hefty fine. There are boxes stationed at train stations - You just have to insert ticket and time and day will get printed on your Bigletti
"Bella" no better than "Nutella"