If I were you, I'd join ISACA.org and research heavily in all the different aspects of IT Auditing. There are behavioral mehodologies you'll need to familiar yourself with, such as understanding and maintaining independence while you're working, knowledge of IT Audit project compoments (similar to Project Management), understanding different types of controls and what they're intended to manage (Detective, Preventative, Inherent, etc...). Heavy security conceptual knowledge is also important, as well as Disaster Recovery and why controls are necessary there as well.
Other options, I would try to get my hands on some CISA Certification test prep guides, which can lay these out in better detail. ISACA has some of these as well, but if you don't wish to join, you can go there and research IT Structures and how they relate to CoBIT (should that be a potential are of futher interest). You can pull down CoBIT mappings they have and study them as well.
I know this is rather lengthy, but hopefully once you start researching these areas, you'd get an idea of what kind of tech questions you might run across. If you know the potential employer's systems that are being used, that would help you focus more on how they work, as well as how to obtain evidence, such as User ID management, Change Management, Application controls, and security controls. The better you understand the systems being in scope for an audit, the better off you'll be.
I hope this helps.
John C. Fielder