Nowadays many interview questions are available in the Internet to help candidates. Most of them check the popular questions and are well prepared with ready-made answers.
Think innovative. Asking mere questions that are already made popular through Internet may not reveal the candidate’s true personality. Instead, you can provide a problematic situation and ask the candidate to resolve the problem. This should be on the spot.
You can even slightly tweak a current issue in the organization and make the question as "How to handle this situation?"
The candidate’s reaction to the unexpected question, approach towards the problem, time taken to resolve it – these things will provide you a lot of information about the candidate.