As you want Guidance for ONGCGraduate Trainee Exam, so I am providing important guidance here:

You will collect study material i.e. syllabus, question paper, important notes etc.

Make a Schedule and follow it

Solve old year question papers

Use short tricks for practical questions

Make short notes for Important Topics

Solve Online Mock Tests also

Time Management is very important

Remember about accuracy

Here I am suggesting you for best Books for ONGC Graduate Trainee Exam:

ONGC Graduate Trainee's Exam Mechanical Engineering Paperback – 2015
by Chandresh Agrawal (Author)
Rs. 333/-
Product details
Paperback
Publisher: Priyanka Prakashan; Second edition (2015)
Language: English
ASIN: B00KDEOSMY

ONGC Graduate Trainee's Exam Executive (E-1) Paperback – 2015
by Chandresh Agrawal (Author)
Rs. 240/-
Product details
Paperback
Publisher: Priyanka Prakashan; Third edition (2015)
Language: English
ASIN: B00KJFFAO2

ONGC Mechanical Asst. Executive Engineering Recruitment Examination Paperback – 2 Apr 2014
by GKP (Author)
Rs. 340/-
Product details
Paperback: 2014 pages
Publisher: G.K. Publications Private Limited; First edition (2 April 2014)
Language: English
ISBN-10: 935144211X
ISBN-13: 978-9351442110