In Italy hitchhiking is a bit less common than in France or Germany, but it's very well possible. It is good to ask people in parking areas or at gas stations. Most of the Italians don't speak English. All you need to know is, that hitchhiking means autostop in Italian.
Just say autostop and your destination or show your thumb, otherwise they often think you are asking how to get somewhere, as Italy has a lot of tourists. Especially in summertime there are a lot of tourists from Austria and Germany. The new European plates start with a letter on the left side of the plate, representing the Country. Most Austrian (A on plate) and German (D on plate) are on the way to the sea or on their way back from holidays. So if you want to go North or South, try to find Germans or Austrians (they also speak better English than the Italians).
You can get a free map of whole Italy at almost every gas station (autogrill) with all gas stations listed in the map.
The northern part of Italy is safer than the southern part.
Italy is in the Schengen treaty.
Take the Highway A23 (in the eastern part of Italy) to Austria (don't try to hitchhike through Switzerland, it's very difficult). Follow the A23 to Villach and Salzburg to get through the Alps very easy. On that way, you will also find a lot of people heading to Hungary, Slovakia and Slovenia.