A good inquiry question meets most of the following criteria:

• relevance to the learner
• open-ended and higher-order (have no right or wrong answer)
• answers are not already known
• multiple possible answers
• not too personal
• cannot be answered without careful and lengthy research—answers have to be more than simple facts
• able to be researched given the available resources—must be answerable
• encourage questioning of basic assumptions
• promote further inquiry

(list adapted from http://www.scholastic.ca/education/teaching_tip/march2013.html)