How do I phrase questions in Italian?

Differently from English, in Italian the phrasing of the sentence does not change if it is a question or a statement.

In writing, simply add a question mark at the end of the sentence to make it into a question.

For example: "Hai mangiato." is a statement. "Hai mangiato?" is a question. 

While speaking, intonation is the key. Rise your intonation towards the end of the sentence to signify that you are asking a question.