As per my experience with PSUs examinations, knowledge doesn’t matters but the practice of the trendy questions. I am sure when you will attempt several PSUs exams you will become familiar with those sections and type of questions they ask. Actually there are some standard books that you should go through and do the practice of it’s questions as much you can do. Like I am from ME background and believe me I have referred only “PSUs Mechanical Engineering” by Made Easy apart from that I gone through the basics from some standard books that’s it . But before any examination I just go through that book it’s sufficient for me to revise before examination. So look for such a book and start preparing.
I my self got disqualified in ISRO and NTPC exams last time as the order of examinations were, ISRO->NTPC->NPCIL->BARC->SAMEER->BHEL. I got selected in last four exams. So once you get a flavor of those questions you will be able to qualify several exams.

for further details about PSUs exams written and interview experience please visit:
http://www.pjbindass.com
you can contact me on:
smr_psus@yahoo.in
8423588028

Wish you all the best for exams and other future horizons!!

ntpc, bhel, ongc, power grid

NTPC – AIR 312
IOCl – Score 779