Written test was completely non technical, basically aptitude based questions. 40 questions were to be answered in 60 minutes or so. The questions were very general and general knowledge based.
For example, what will happen to the weight of iron, after rusting. Whether it will decrease or increase?

The shortlisting criteria was based on OGPA, since NMDC is a PSU. The criteria was 7.25 OGPA..

Technical Questions:
1. What do we use for lubricating the rim of a bicycle or a motorcycle? Greece or Oil? What is the difference in them?
2. Draw a diagram of the chain assembly we use in cycles/motorbikes?
3. What are the basic mechanical components/equipments used for power transmission? Tell some electrical ones too?

See, the interview taken my the interviewers completely depends on the choice and the mood of the panel. In my case the interview was 90% HR. Whereas, on the other hand, some of my friends had a complete technical encounter. In my case the questions asked were as follows:
1. Tell us about yourself?
2. Why did you change your branch from Mathematics & Computing to Mechanical Engineering, while former being the better one. (Here you can explain your passion for mechanical as i did)
3. what transformation did you ever bring in your campus or career?
Note: The above two questions were based on my answer to the first question.
4. Did you find maintenance a tough job, if not then why?
5. Why do you want to join NMDC?
6. Your interest are more in the field of research and software, then why to join a technical company like NMDC?

Well, i would only say that never panic and always be very confident when you face the interview panel. Also, if you don't know the answer of any question say "I Dont Know" rather than saying something stupid or anything. This will create nothing more than a bad impression. Also, try to have a decent GPA, good will definitely be better. Try to drive the interview on your own, don't be driven by them. I mean to say, alway end your answer at a point, which lead to a question which you want that interviewer should ask you,

Selection process consisted of two steps:
1. Written Test (Non - Technical)
2. Personal Interview

Since the no. of applicants writing the test were around 12, so there was no elimination in my case. They took the interview of all the students. Among those who appeared for the interview my rank was 3rd. 5 of us got the offer.
I think the following factors played an important role in my selection:
1. Definitely a good GPA, as PSU normally entertain people with good GPA.
2. My project work. I mentioned my about my project work a lot of time.
3. My achievements, like changing my branch, extra curricular activities.
4. Self Confidence id Must.