I think the questions asked would depend on the specific department that is interviewing you, so try to do more research about them where possible. Meanwhile, I think it won't hurt to look at blogs or forums discussing educational issues, and check out the news section on MOE's webpage.. Of course, think of how to sell your strengths to tailor to the needs of the specific department, be aware of the recent policy trajectories of the ministry and be sure of why you want to join and how you may contribute.