Gate examination mainly tests the basic ability of the candidate to know what extent he/she has understood about the topic and how well he/she can simplify the problem related to it. And to prepare for it one need not essentially enter into the complex domain of Engineering Subjects but one need to know clearly what/how/why questions as much as possible about the topic of the subject. And that can be put up in single line as “Believe in Basics with clear understanding” is enough to crack the Gate examination.
And about preparation:
Gate preparation can be done by taking coaching or self-study. And taking coaching depends on how and where you’ve studied your Engineering. If you’ve studied in NIT’s or any other bigger institutes where you might have followed some standard books for your academics then one can say that you need not go for special coaching if you really are intended to crack it. I mean if you’re determined to Crack the Gate examination any institute student it might be, can crack without any coaching. Generally people might be not able to find time for extra coaching so it’s probably not necessary. But if you’ve enough time then it’s like good thing to take coaching because there you get a clear idea about the Gate examination.