Which preposition should I use?

When do you use the preposition "a" vs "in" in italian?

• for example, andare ____ casa andare ____ Roma tornare ____ Italia fare un giro ____ macchina I don't need for these to be answered as much as I need an explanation on how to know when to use which.

• Answer:

  "andare A casa" -- this one is really common, so it's good to memorize it. "andare A Roma" -- when talking about going TO cities or staying IN cities, you have to use "a" Ex: Siamo stati a New York. Quando andate a Parigi? "andare IN Italia" -- when talking about going TO countries or staying IN countries, you have to use "in" Ex: Quanto costa per andare in Giappone? For methods of transportation: "in" tends to be used for mechanical vehicles, while "a" is used for organic things: andare IN macchina -- go by car andare IN treno -- go by train andare IN bicicletta -- go by bike andare A piede -- go on foot andare A cavallo -- (funny I know, but) go by horse