Ask "How?" Not "Why?"
One of the tricks mentioned by Becker in Tricks of the Trade is Ask “How?” Not “Why?” which comes under Imagery. He says that everyone is familiar with this trick but do not use it, they tend to ask “why” because it is more natural. He said, “Somehow “Why?” seems more profound, more intellectual, as though you were asking about the deeper meaning of things, as opposed to the simple narrative “How?” would likely revoke. “ (p.58)
I think asking “How?” is a scientific approach, it shows that you are trying to figure out the answer for the question. The question, “Why is the sky blue?” asks for a reason. While the question, “How is the sky blue?” is like a query. I think “How?” question gives you a broader scope for answer and it is a question a scientist would ask.
Becker says that in his research, the “why?” questions provoked a defensive response. People thought they had to justify themselves by giving appropriate reasons. Such response was not found when he asked the “How?” questions. People gave detailed answers to the questions and did not give the justifying answers. The answers were not short like the responses with the “Why?” questions. But then he mentions that both the questions are necessary. Sometimes your research may ask for much detailed information from your subjects and sometimes you need only the specific details that are obtained with the “Why?” questions. Depending on the requirements of the research, you may choose between the “How?” and “Why?” questions.