Make sure you study the competences on the job advert letter, as that will be what would be asked from you. There are several competency in the UN, we have Communication,Professionalism, teamwork, etc. Make sure your study different questions on each compency that was advertise in your Job Opening. That will help you, in answering your questions very well. Make sure you also tell them what you could have done better, or a lesson you learnt from each expereince. If you a progrmas person, remember to always mention how you ensured Gender representation in your role.

They called me 4 weeks after the written test. Interview lasted around 40 minutes. It was led by a panel. 3 people, including an HR representative. No technical questions were asked at all, as it was purely a competency based interview.