The question “Who speaks Italian?” uses the pronoun who as a subject. Just like in English, the Spanish question ¿Quién habla español? uses the pronoun quién as the subject.
These questions are created exactly the same in Spanish and English. However, since there are both a singular and plural version of who in Spanish, there is one thing you don't think about in English that you'll have to think about in Spanish. You know that you're supposed to conjugate the verb “to go” with the subject. When the subject is a question word, the verb is conjugated in either the él/ella or ellos/ellas form based on whether the question word is singular or plural.
The singular version of “who,” quién is meant to represent one person, so use the él/ella form of the verb you would use if one person were the subject of the sentence. The plural version of “who,” quiénes, is meant to represent several people, so you would use the ellos/ellas form of the verb with it. When the question words quién and quiénes are used without prepositions, they always will be the subject of the sentence. Here are examples of quién and quiénes as subjects of a sentence:
¿Quiénes aprenden español?
Who learns Spanish? (assuming that more that one person is learning Spanish)
¿Quién baila con María?
Who dances with María? (assuming that only one person is dancing with María)
Notice that when the question word serves as the subject, there is no need to switch the subject and verb.
A few other question words can act as the subject of the sentence too, such as cuánto and cuánta. Be careful to consider the gender and number of the noun that cuánto represents. For example, if you already established you were talking about rain (la lluvia), you could say:
¿Cuánta cae cada verano? ( cuánta is the subject, cae is the verb)
How much falls each summer? ( how much is the subject, falls is the verb)
The question word cuánta can be used in another type of question. This is simply a yes or no question with the question word placed in front. For example:
Does Marta eat meat? ( Marta is the subject, eat is the verb)
¿Come carne Marta? ( Marta is the subject, come is the verb)
You can also put the question word “how much” in front of this yes or no question:
How much does Marta eat?
¿Cuánto come Marta?
In the example above, you could also say “How much meat does Marta eat?”
¿Cuánta (carne) come Marta?
Here ¿cuánta? is used to refer to la carne, not that fact that Marta is female.
The question words cuál and cuáles are also used to ask questions.
What's today's date?
¿Cuál es la fecha de hoy?
Which songs (which ones) do you prefer?
¿Cuáles canciones prefieres?