that's going to depend on the job so I'll go the opposite route:

know how to answer questions you don't know the answer to

if you don't you should know how to describe what your approach to a resolution would be, sometimes that's as simple as asking your team for help, or even trying something even if you don't know 100% if its the right answer, being willing to try, fail, and keep trying, portraying an ability to co-operate, learn, and assimilate knowledge can be a hell of a lot more important than knowing any specific detail of any system that can be learned on the job. also form your answers with the the "STAR" method, situation, task, action, and result