The questions can range from a variety of topics. If you have worked with ITOM then you should also be good with sys administration and development plus have good hands on on MID Server, Discovery, Service Mapping, Event Management and Cloud Discovery to say the least.
If you have attended ServiceNow certification tranings you can go through the Administration, Developer guide and refresh key topics there. However regarding MID Server, Discovery, Service Mapping, Event Management and Cloud Discovery you need to have a good hands on as you will be probed on how experienced you are on these modules.
