Explain the difference between open and closed questions. A closed question has a limited number of possible answers. For example, a "yes or no" question is a closed question. An open question can have any number of possible answers. A question starting with "why" is almost always an open-ended question.
Practice open and closed questions by having the students ask their own versions to verify they understand the difference between the two.
Give examples of focusing questions, which is when you start with general questions and then narrow the questioning down to get more and more detail about a subject.
Ask a student to tell a true story in three or four sentences. Then have students ask focusing questions. For example, if a student tells a story about a camping trip, focusing questions could find out how many people were there, the ages of those people and then the specific names of the people under the age of 18.
Read the opening paragraph out of newspaper stories and then have the students ask questions about the articles. Provide answers based off those questions if that information is available in the story. If it isn't, discuss why that information may not be in the story.
Review the importance of "who, what, when, where, why and how" in regards to news stories and subjects in general. Students should be asking those questions on subjects when the information isn't given to them.