This is a great question. It is best to start with a definition of what an indirect question is. An indirect question is a question that is reported by another person. An example would be: "John asked Mary who broke the cup."
In Latin, there are three key elements you need to keep in mind.
First, you need a "head" verb. This is a memorable way of saying that you need a verb that you usually do with your head - - think, ask, say, imagine, and the like.
Second, you need a word that introduces the interrogative, such as words like, quis, quam, ubi, and the like. These words make the indirect statement into a question.
Finally, you need a subjunctive verb in the interrogative statement. In other words, the verb that follows the interrogative word is always in the subjunctive.
Here are two examples:
Rogat quid faciat. "He asked what she/he was doing."
Nescivit cur non dixissent. "He was ignorant why they has not spoken."
Notice the two "head words" (Rogat and Nescivit). The interrogative words are Quid and Cur. And finally, the two verbs are in the subjunctive mood.