Before answering the question, just to add credibility to my answer let me tell you, I’ve been there, done that.
Intel – selected in Internship interview in first attempt.
Texas Instruments – selected in campus placement written test and interview (look here for the story: Is cgpa important for placements?)
Qualcomm – made it past written test, did not attend interview as TI results were already out.
Below I share my thoughts from my experience of preparation for VLSI written tests and interviews. So, my answer is more from a campus placement point of view.
1. Groundwork: Understand the significance of different VLSI job profiles
Getting good at RTL coding may not be needed if you are interviewing for backend profile.
Getting good at analog electronics is not that essential if you are interviewing for a digital profile.