PICO is the acronym used in health sciences to develop a good clinical question. 

P Patient, Population and/or Problem 
Think of this as what is common about the subjects studied.  Perhaps the population is as simple as “people with migraines”; although that’s going to be a very broad population.  Perhaps it’s “post-menopausal women with aura-type migraines.” You might find that’s too narrow when you search.  

I Intervention 
What are going to do, if anything, to treat the patient?  

C Comparison 
Compare one intervention to another (or multiple interventions) including null interventions (doing nothing) or standard care. 

O Outcome 
What is the desired outcome? These should be patient-oriented more than disease-oriented. 

T Time Frame or Type of Study
What time periods should be considered?  What study types are most likely to have the information you seek?  What clinical domain does your question fall under?