We all know the most dreaded part of an investment banking interview is the technical questions. Sure, you might be terrified of faking your way through the cultural fit stuff when you secretly hate the place, and yeah, you might be afraid of getting a question with no good answer, like, "If this is your dream job, then what happens if another firm gives you a better offer in five years?" Those are rough. But if you don't know what to say when some hard competency questions come your way, then you're dead in the water.
Certain technical questions are relatively easy to prepare for, like "Walk me through a DCF" or "Explain the three types of financial statements." You can study for those in a pretty straightforward manner and practice demonstrating your competency until you're blue in the face. Basically, if you actually get it, and you know how to talk, then you can do it.
What's harder is coming up with answers on the spot to interview questions about more specific modeling examples. At it's core, it's the same thing, but you have to attune your mind to applying your knowledge to particular cases on the fly. Part of it comes back to competency, but a lot of it is nerves, or calming down and trusting yourself to work through the problem.
Take the Quiz: 10 Financial Modeling Questions From Investment Banking Job Interviews